Last Updated: 12:00PM BST 14 Apr 2009  Turned out nice: Maria Fitzpatrick produces a perfect tortilla under the watchful eye of Basque chef Nieves Barragan Photo: ANDREW CROWLEY  It’s easy to think of eggs as destined only for breakfast or baking. They’re rarely given main meal status. But with the right treatment, the humble egg can provide a savoury, satisfying dinner that would impress the most discerning palate – as I learned when I took a lesson from Nieves Barragan, the head chef at Fino, a Spanish restaurant in London. Nieves comes from the Basque region, and from a culture where eggs are the hero ingredient of their hearty signature dish, tortilla, as well as some beautiful tapas and desserts (see recipes).  “Tortilla makes a wonderfully adaptable meal,” says Nieves. “In Spain, we eat it in the evening, with salad. Once you know how to make it properly, you can add to it. Right now, you might incorporate some new-season asparagus, but it works with anything from chorizo to cod.”  First things first, what makes a good egg? Free-range, Nieves says, is essential for depth of flavour. Chickens fed on grass tips tend to produce more deeply coloured yolks, which can transform a dish. But size matters, too, she tells me, as she deftly cracks 10 into a bowl in as many seconds. “My mother always told me: medium eggs only. Larger ones have more white, and a less rich flavour.”  After eggs, the most important ingredient is time. Too much or too little can be the downfall of this dish.“Don’t rush the frying of the onions,” advises Nieves, “they need to caramelise slowly. All the water should evaporate.”  The finely sliced potatoes, too, need to turn golden brown all over or they will absorb too much egg, and make a “heavy” tortilla. Another classic mistake is whisking the eggs for too long. Nieves stops me after about 30 seconds, when I would have merrily whisked away for ages. “Your eggs should remain quite firm and full-bodied, not watery. Once they become liquid, they won’t 'hold’ the other ingredients and will stick to the pan.” The trick is to stop while they still look orange, not pale brown.  To achieve the delectably sweet marriage of onions and potatoes, the thinly sliced potatoes (like soft potato crisps in appearance) are added to the onion when it is extremely hot, so that they absorb the maximum flavour. Even my stirring needs serious attention. Nieves shows me how to lift the mix from the outside of the pan and toss it together, to avoid mashing the ingredients and creating clumps.  At each step, the ingredients are given time to rest, for flavour to develop. While I’m whisking, the hot onions and potatoes are sweating in a cling film-covered bowl (steam binds in the flavour). The eggy mixture is left for a further five minutes for the egg to be fully absorbed.  “Waiting makes all the difference,” Nieves explains.  Ultimately, getting a non-stodgy tortilla means achieving a slightly gooey consistency inside. “Don’t be afraid to test it with your hands, and keep checking both sides,” advises Nieves.  I tend to my tortilla by closing in the edges with a spoon once turned, and pressing at the centre for a gentle hint of ooziness.  Guided away from the pitfalls, I turn out a tortilla that irreversibly heightens my expectations of eggs. Following the rules, it’s surprisingly easy. This is a beautiful blend of savoury and sweet, melt-in-the-mouth and wonderfully light yet substantial. Not bad for an ingredient you’ve probably got just waiting in the kitchen.
Eggs aren&rsquo;t only for breakfast. Maria Fitzpatrick learns how to make more of    this humble ingredient