Until recently, there used to be a workman's cafe just off the Portobello Road that was run by a Spaniard and his wife. I say a workman's cafe, but, in truth, it had something of an identity crisis and couldn't quite decide whether it was a greasy spoon, a tapas bar or an Italian cafe. But blokes were kept happy by the full cooked breakfast while babes could drink cappuccino and smoke a cigarette sitting at the bar. And for the seriously hungry there was the Spanish omelette.

This was made fresh every morning, so that come elevenses, it was sitting on the counter still warm from the pan, a perfect disc patched with gold, just the thinnest tender outer coating of egg and, inside, a voluptuous mass of fried onions and potatoes.

I was regularly cajoled by my husband and his friends into trying to make one "just like Toni's" at home. And even though Toni assured me there were no secret ingredients, just eggs, potatoes and onions, mine never came up to scratch. After half a dozen attempts, I finally went to Toni on bended knee and begged for a lesson.

I am very glad now that I did because the cafe has since closed. I hope, despite the rumoured tales of woe that had befallen him, that Toni sold it for a fortune and is leading the life of Riley back in Galicia. Certainly, his Spanish omelette is the finest I have tasted.

I should, of course, be crediting his mother: it was she, after all, who taught him. But be warned when buying tortilla. It may be served at every tapas bar in Spain, but unless it's still moist and creamy in the centre it can be worse than dull.

Toni's Spanish Omelette, serves 2-4

This is a Spanish omelette at its most basic. You can add some slivers of ham, sauteed wild mushrooms, cooked peas, chopped herbs and the like. I also like to eat it with some warm garlic cream spooned over or a dollop of hollandaise.

2 small onions, peeled, halved and sliced

4 medium-size main crop potatoes, peeled, quartered and thinly sliced

5 large eggs

Extra virgin olive oil

Sea salt

The first point my tutor was keen to drum home was the importance of cooking the onions and potatoes together. In truth, this isn't the easiest operation as the potatoes tend to stick to the pan, so you have to be quite diligent. But the way they infuse each other with their flavour is well worth that extra bit of attention.

Begin by putting a few tablespoons of olive oil in a frying pan and cooking the onions and potato together with a generous smattering of salt for 25 minutes over a low-ish heat, turning frequently to stop them colouring on the bottom. Now cover the pan with a tightly fitting lid and cook for another 10 minutes over the lowest possible heat to gently steam the potatoes and ensure they are cooked through. Transfer to a bowl and, once they are cool, break in the eggs and lightly stir with a fork, then season the mixture.

Heat a little oil in a 20cm frying pan and when it begins to smoke tip out the excess. Poor in the omelette mixture, turn the heat down low and scramble until it absorbs the oil and begins to thicken. Keep shaking the pan and loosening the omelette to prevent it from sticking. After two to three minutes, turn it over. The easiest way to do this is to slop it onto a plate and then invert it back into the pan, although if you fancy yourself as a pro, you could always flick it.

The underside should be mottled a light brown. If any egg has stuck then scrape this off. Re-oil the pan in the same way as before and then return the omelette to it and cook for another two to three minutes, pressing the centre, which should remain yielding and soft to indicate a runny centre. If it is hard, then the egg has overcooked. Err on the side of caution and, if unsure, slip a knife into the centre. The egg shouldn't be oozing out but you should be able to see that it is wet. As it cooks tease the sides into a neat rounded edge. Serve it in wedges straightaway.

If you intend to eat the omelette cold then cook it over a slightly higher heat, about two minutes each side as it will continue to set as it cools