The knives are out: Chef Mark Hix judges the culinary efforts of our food critics Tracey MacLeod and John Walsh

They can dish it out, but can they take it (criticism, that is)?

For this season's food and drink special, I thought it would be fun to turn the tables on the magazine's two restaurant critics, Tracey MacLeod and John Walsh, and see how good their cooking skills are under pressure. I devised a Masterchef-style, fiendish and competitive cook-off, which involved them both being given the same ingredients and asked to come up with an idea for a dish and cook it.

So I assembled two sets of identical ingredients – seabass fillets, best end of lamb, ceps, sprouting broccoli, leeks, cauliflower, butternut squash and potatoes – and asked Tracey and John to create a dish each using as many or as few of the ingredients as they wanted.

The location for the cook-off was The Library, my private demonstration kitchen at Tramshed, which has two cookers, two ovens and all the kitchen kit you could wish for. John and Tracey also had to hand store-cupboard ingredients and all the basics.

Tracey went for the lamb, assembling a colourful, varied set of ingredients which looked promising, asking for lots of extra ingredients and herbs, which only made John appear more nervous.

He eventually settled for fish, potatoes and broccoli, adding chorizo for interest, colour and texture in the same sort of way that you would use bacon with fish – a simple and delicious idea. They prepared very different dishes; read on to discover how they fared, as well as my verdict on their final creations.

Tracey cooks: Herb-crusted lamb, spiced lentils, roasted root vegetable quinoa and gremolata

Competitive? Of course John and I aren't competitive. We're colleagues. Compadres. Friends. So when our editor suggested that we go head-to-head in a cook-off, a Hix-judged spin on the feared Masterchef invention test, my first thought was, "That sounds like fun". My second thought was: "How can I really freak John out and make sure I win this thing?" I immediately requested a sous-vide bath, a tatami mat and some liquid nitrogen, just to get him sweating.

On the day, of course, no extra equipment was needed to work us both into a state of high anxiety. What's the collective noun for a brace of restaurant critics in a flop-sweat of reputational panic? That was John and me, reporting for duty in the gleaming show kitchen above the Tramshed. It wasn't so much each other's judgement we feared; it was that of Mark Hix, who is an actual chef, and would surely discover that his opinionated fellow columnists aren't in any position to criticise the cooking of others.

With our game faces on – ie, please Mark, don't make us cook game – we squared up over the mystery ingredients. My immediate reaction: phew. No tiny birds to pluck, or whole fish to gut. The rack of lamb looked good. The basket of wild mushrooms looked frightening. We both made a bid for the purple sprouting broccoli. "Hmm, I might do that with some drizzled sweet tahini," I announced, just to mess with John's head. "Oh God…" he groaned. Mark chipped in with, "Which one of you wants to use the steam oven?" "Oh God," we both groaned.

Soon we were blindly grabbing things out of the basket like contestants on Supermarket Sweep. John went for fish. I went for lamb, just to be different, and because I couldn't think of a way of making seabass exciting. In a version of the classic movie tooling-up sequence, we prepared our stations. Knives were chosen, sauté pans weighed up, aprons tied. Then, eyes narrowed across the range, we faced off.

Ignoring the golden rule of dinner party cooking – never try anything you haven't made before – I decided to roast the lamb with a herb crust. Fresh breadcrumbs were located in Mark's larder (grate your own breadcrumbs? Not in this dream kitchen) and mixed with chopped thyme and lemon zest. Now, how to make them stick to the meat? Mark immediately sprang forward with a vat of mysterious dark jelly, produced from the dark corner where he keeps the special stuff. "Grape must mustard," he explained. I slathered it on. What is it? Who cares? As long as he likes it, and he's judging this thing, I'll use it.

With the lamb in a hot oven I started on my vegetables. Butternut squash, cubed and rubbed with olive oil, salt and cumin seeds, went in to a roasting pan with shallots and whole cloves of garlic. I started sautéing onions with cumin and coriander for the spiced lentils. A request for dried chilli got Mark truffling excitably around in his 'Asian drawer' and producing five different varieties. Thankfully he didn't seem to be taking his judging duties too seriously, supplying a whole chorizo sausage from his freezer for John, who left it sitting between us to defrost in a bowl of warm water, winking at me like a long, pink challenge.

So helpful and unjudgemental was Mark, that at one point I found myself grandiosely giving HIM hints about the best way to cook quinoa – it's important to toast it in a dry pan before adding boiling water, just to bring out the nuttiness… In the TV show, this would be the bit where I burnt my hand and got taken away in an ambulance, sobbing.

I was aware, as I chopped and stirred, that John's state of mind couldn't be characterised as 'quietly confident'. Oscillating between low moans of despair and increasingly desperate calls for a steamer, he didn't seem to be enjoying himself. His ultra-cautious approach to pan-frying his fish eventually provoked Mark to intervene. "What are you doing there? It looks like you're warming some fish in a pan – very slowly."

Otherwise, our judge largely maintained a polite silence about our efforts, although at one point, surveying the chaos of pans, knives and fingernail shavings scattered about my station, he suddenly piped up, "Will you say in the article that we offer cookery classes here?".

Ninety minutes after we started, we were ready for service. All the mistakes I've regularly criticised others for making, I had blithely made myself. f I'd wildly over-seasoned, on the grounds that chefs have hardly any tastebuds left. I'd crowded too many ideas on to my plate and drizzled the whole thing with a powerful gremolata of garlic, lemon zest and thyme. And I had undercooked the lamb. How do you like it? I asked Mark. "Just a little bit pink," he replied. I decided to serve him the two marginally less bloody end cutlets, which couldn't be arranged symmetrically on top of the vegetables. Oh well, drizzle, drizzle.

Meanwhile, John was calling for a piping-bag to pimp his mash. "Don't overbeat," I murmured, in a last-ditch attempt to psych him out. The plating-up felt genuinely tense; we needed to coordinate our dishes so they were both ready for their close-up. John called urgently for white wine. I turned, expecting to see him deglazing a pan, but he was pouring himself a large glass.

The finished dishes looked like the first and last plates in an encyclopaedia of modern cooking. John's oozed sophisticated Galloping Gourmet smoothery. ("Very Seventies! Very vintage!" cooed our editor encouragingly.) Mine looked colourful, but… busy. "Do you want to replate that?" ventured Mark. "It looks like you've dropped it."

He tried John's first. A mouthful of fish, a few molecules of potato. "Delicious!" he said guardedly. Then he turned to mine. A tiny sliver of lamb, a few grains of quinoa. "Delicious!" Come on Mark, you have to say more than that, chivvied our editor. At a push, he reluctantly admitted to preferring my boiled purple sprouting broccoli to John's steamed version with cumin seeds, but that was it. Turns out Mark is much too nice to criticise anyone else's cooking. So with some relief all round, we'll go back to doing that, and leave the cooking to him.

Mark's verdict on Tracey: This looked good in terms of texture and colour. Tracey has added variety by using store-cupboard ingredients such as lentils and quinoa along with spices like cinnamon and cumin – some good combinations going on here. The lamb is nicely pink and the gremolata adds a nice zing. Overall, very good – reminds me of Ottolenghi.

John cooks: Roasted fillet of seabass with chorizo, ceps, broccoli and piped mashed potatoes

Thank heavens for Doctor Johnson. He justifies the existence of the restaurant critic. "You may scold a carpenter who has made you a bad table, though you cannot make a table," he said. "It is not your trade to make tables." And in your reviews you may tick off a chef for an inexpert crème brûlée, though you wouldn't have a hope of brûlée-ing one yourself. So when Tracey MacLeod and I were offered a Masterchef challenge – to cook a dish from scratch, to a deadline, using ingredients supplied by Mark Hix – did we worry that our critical reputations were on the line?

Of course we did. What are you, nuts? The atmosphere in the upstairs kitchen at Hix's Tramshed restaurant in trendy east London was raw with competitiveness, as we sorted through the ingredients: seabass, two racks (sorry, 'best end') of lamb, a huge cauliflower, onions, shallots, potatoes, butternut squash, two kinds of mushroom, parsley, cream, wilted purple sprouting broccoli, leeks and small bowls of chicken jus – which clearly wouldn't harmonise with the fish or the lamb, so thanks for that, Mark…

Knowing Tracey's a sophisticated cook (whereas my style suits the palates of small children and squaddies), I didn't fancy a lamb roast-off. Too humiliating. OK, I said, why don't you dof the lamb, and I'll do the fish. Fish is easy-peasy, isn't it? Melt butter with olive oil, cook on medium heat, skin-side down, for five minutes, flip it over, five minutes more, take off heat, poke to see if it's done and bingo, Mark and I are off to the pub to discuss my future in his kitchen.

I looked over at my rival. Her brow was furrowed with concentration, as lamb recipes from the world's cookbooks hurtled through her brain. "I'm going to need some extra things," she said, like a surgeon surveying an inadequate table of forceps and scalpels. "Mark, can you find me some rosemarybreadcrumbslemonbutterlentilscinnamon…"

Bloody hell. While I was planning to dish up boring plain fish (and, er, mash) she was planning a 19-flavour extravaganza. I thought fast. What was a pungent spice that flavours vegetables?

"Got any cumin?" I asked Mark Hix.

"…oh yeah, and cumin too," said Tracey.

This was so unfair. "Have you any chorizo?" I countered. Tracey was shocked. "You can't just ask for another main ingredient," she hissed. "You might as well say, 'Got a roast chicken I can use?'." But she was overruled, on the grounds that chopped chorizo was a flavour component rather than a central item.

We chopped and peeled, sliced and sluiced, opened cupboards, banged drawers, grabbed saucepans, wooden spoons and fish slices, bent to our work like jockeys. We lit the cooking hobs, trying to be first to fry chopped onions and look professional. We demanded more utensils, like cuisinal prima donnas.

My notes are covered in oil-spots, but they're mainly about timing: 20 minutes for the potatoes, 10 for the fish, seven for ceps seething in butter, five for the broccoli to steam with a little cumin. The seabass looked gigantic – more like a basking shark – but Hix explained that you cram it in the pan by slicing through the skin and folding the tail over to rest on the upper section. Sweating from this physical manoeuvre, I looked at Tracey. Somehow, out of nowhere, she'd magicked a perfect herb crust on to the lamb rack and was serenely (even – could it be? – a touch smugly) sliding it into the oven.

I fried chopped shallots and chorizo, hauled them out and cooked the fish in the sexed-up oil. With a plain white fish like bass, your nerves are on alert: the heat should be high, but you must turn the fish over before it sears; you check the white side is done by prodding rather than slicing. You mustn't take your eyes off it. It's an emotional 10 minutes.

Hix prowled around, doing that eyes-widened-with-incredulity trick perfected by Michel Roux Jnr on Masterchef. He looked on as I added cream to my perfectly cooked mushrooms, didn't agree with my decision to steam the broccoli, barely glanced at my perfect bass, and winced as I folded chopped shallots into the mash. Then I had a brainwave. "Have you," I asked, "a piping bag?"

I was having a mental flashback to the seabass I ate in J Sheekey years ago. It arrived with piped mash arranged round the fish in scallop-y ridges. Hix showed me how to transfer the mash into the bag, attach a nozzle, and pipe away. But it didn't come out in bursts of artfully ribbed loveliness; it came out like toothpaste. Twice or thrice I ran it all the way round the bass. When I stopped, it seemed an awfully white dish: actually it was the colour of putty. The creamed mushrooms added a coffee hue to the latte-coloured plateful, although the broccoli helped.

Tracey, meanwhile, had knocked up a gremolata (whatever that was), diced butternut squash and served it with cinnamon, carved her herb-crusted lamb and artfully arranged two teensy chops across each other, mid-plate, as smartly as though she commanded the pass at the Savoy every night. My fish actually tasted pretty good, I thought; so did the mushrooms; ditto the mash. But it was eclipsed by Tracey's lamb – a sublime dish, with five vivid flavours flapping about the rough-textured meat like attendant fairies.

Clearly I'd spent too long worrying about the timings and not enough on adding flavour-value. I'll know better next time. Whaddya mean there won't be a next time? Mark? Mark?

Mark's verdict on John: This all looks terribly retro and Fanny Cradock-ish. John has made good use of the piping bag to pipe his mash round the fish. The fish was delicious, really well cooked and he's done very well to use the chorizo in the same way as you would bacon. It all goes well with the creamy mushrooms and steamed sprouting broccoli.