Sushi may be the ultimate in sophisticated grab-and-go lunches, but making your own nigiri is surprisingly simple. Alice-Azania Jarvis develops her raw talent

Last Christmas, I requested a Japanese cookbook. It seemed like the sort of thing that might come in handy. After all, I like sushi. Who doesn't? All those tasty little mouthfuls of rice, seaweed and fresh fish. And everyone knows that Japanese is king among restrained regimes: low in fat, high in Omega 3s. Come January, I thought, my clogged up arteries and alcohol-soaked bloodstream would welcome the relief. I would become a sushi whizz and much healthier for it.

Tragically, none of this came to pass. Instead, the book was laid on my coffee table, where it has remained untouched save for the gentle caress of the numerous magazines, envelopes and notebooks that have accumulated on top of it. Never mind, it had all seemed rather complicated anyway: lots of skilful rolling and obscure ingredients. Not the sort of thing one needs in our time-poor, pasta-and-sauce lives. Perhaps sushi was best saved for restaurant meals and grab-and-go lunch breaks.

Now, however, Henryanto Aloysius is trying to change my mind. "I guarantee that in two hours' time you will know how to make sushi. It's easy." His enthusiasm's infectious; his confidence less so. He leads the weekly "Sushi 101" class at Kensington's Whole Foods Market, where I am standing in front of a chopping board and a neat pile of ingredients.

Ironically, sushi was first popularised as a convenience food. Wrapping fish in rice was a common preservation method in ancient South East Asia. Hundreds of years later, variations on the practice had evolved into a quick and easy fish-and-rice meal, handy for the harried population of Tokyo. Nowadays, it assumes a range of forms, thanks in large part to the creativity of California's Japanese immigrants, who fused their food with American produce, creating the famous California Roll of cucumber, crab and avocado, as well as a host of chicken and duck dishes. For the purpose of the lesson, we've been provided with vegetarian options (avocado, carrot, cucumber) and cooked fish (smoked and grilled salmon, and prawns). Raw fish may be more authentic, but the cooked stuff is more straightforward: easy to find, and without any "am-I-going-to-wake-up-with-food-poisoning?" anxiety.

But first: the rice. Surprisingly, this is rather complicated: lots of washing, rewashing, soaking, boiling and dressing. The dressing, it seems needs to be made just so: a mix of rice wine vinegar and sugar reduced to a syrupy liquid and sprinkled over the rice. I suppose if you were making this at home you'd just have to create this in the morning, or the day before – a bit like making a pizza base. It's the prep before the fun.

The fun, of course, is the rolling. It is also the bit I've been dreading. I'm not the most dexterous of people at the best of times, and I'm entirely incapable of performing any task that requires even a modicum of precision. The most important thing, says Aloysius, is the right utensils: a freshly-sharpened knife, a clingfilm-covered bamboo mat (easily attainable from supermarkets and specialist stores; ours came free with the lesson), a damp towel with which to wipe the knife before each slice, and some nori (dried seaweed) sheets, also relatively easy to find.

Step-by-step, he's right: it's much less complicated than it looks. Take a handful of rice, the size of, say, a tennis ball, and dab it on to a sheet of nori, which immediately sticks to it. Plop the pair, seaweed first, on to your mat and flatten the rice ball, spreading evenly over the nori, leaving about a centimetre of bare seaweed running along the length of the sheet. Once that's done, all you have to do is pick your fillings and roll.

The trick here is not to overfill: the more streamlined your roll, the less likely it is to burst at the seams. I decide to stick with the classics: salmon and cucumber, prawn and avocado, that sort of thing. A few in the class embrace their creativity, though I remain unconvinced as to the wisdom of pineapple and spinach sushi (or anything for that matter). After laying out your combination in a horizontal line along the centre of your rice, it's just a matter of lifting up one side of the bamboo mat– holding on to the sheet or rice as you do so – and rolling, so the rice wraps around the filling. It feels like everything should collapse but somehow it doesn't. The stickiness of the rice, the basic mechanics of your mat; something ensures it works. You finish rolling by using your mat to wrap everything up and voila, it's done. If it doesn't look neat enough, just wrap the bamboo round again and give it a good squeeze. I'm sure mine won't work but mysteriously it all comes together. It's not as hard as it looks.

Once we get the first roll out the way, we're almost as confident as Aloysius. We begin trying our hands at other things – the inside-out roll, which basically just inverts the seaweed and the rice, and feels even less like it should work but does – and the hand roll, the Japanese equivalent of the sandwich, conical and created so that sushi chefs could eat quickly with one hand, on the job. By this stage, we've attracted quite a crowd. Situated in a far corner on the top floor of Whole Foods' Kensington flagship, our class had pulled in an army of spectating shoppers; clearly I'm not the only one who thinks sushi is beyond their grasp. By the end of the class, we were rolling confidently and slicing fairly neatly (the trick is to saw very, very slowly without applying pressure on the roll), packing away our creations in little takeaway boxes for dinner. I, it transpires, am not to need mine. Just before we leave, Aloysius announces – to considerable bemusement – that he plays a game with his pupils at the end of each lesson. He's hidden a coin under our chairs. And what do you know? There, stuck to the underside of my stool, is a 10p piece. I've won a vegetarian sushi platter fit to feed an army. So much for restrained cuisine. Still, this won't be my last time making sushi: as well as the bamboo mat I've been given a glossy instruction manual. I may not be the paragon of virtue promised by Christmas last, but perhaps I'm finally getting there.

Sushi rice

3 cups short grain rice (white or brown)
31/4 cups water
1/3 cup rice wine vinegar
3 tbsp sugar
1 tbsp salt

Put the rice in a bowl and wash, repeating until the water becomes clear.

Drain, and place the rice in a large pot or rice cooker. Add water, using just enough to cover the rice – don't fill the entire pot.

Allow it to soak in the water for at least 30 minutes – an hour is ideal.

If you are cooking the rice in a pot, cover the pot with a lid and bring to the boil over the high heat. Once the water boils, turn down the heat very low and cook about 15-20 minutes until the water is almost gone.

Remove the pot from the heat and let it sit and steam for 10-15 minutes before serving.

Meanwhile put a small pan on a low heat until the sugar and salt dissolve. Allow to cool.

Spread the hot steamed rice into a large bowl with a spatula. Sprinkle the vinegar mixture over the rice and fold very quickly. Be careful not to mash the rice. Allow to cool.

Inside-out roll

1 handful of vinegared rice
1 sheet dried seaweed (nori)
2-3 slices sushi-grade salmon
2 slices avocado
1tsp sesame seeds
1tbs sushi ginger
Soy Sauce

Place the nori approximately 1 in from the bottom of the bamboo mat. Spread four-fifths of the rice evenly on one side of the nori. Cover the whole surface.

Flip the nori over so the rice is facing down. The nori should still be approximately 1 in from the bottom of the mat.

Spread the rest of the rice, leaving about a third of the surface clear at the other end.

Place the rest of the ingredients at the centre of the nori.

Starting from the end closest to you, firmly roll the mat away from you. When you can no longer see the nori, squeeze the roll firmly in several places to ensure it's tight.