This savory omelet is immensely appealing-but only if someone else is doing the cooking. The typical recipe calls for simmering the potatoes in up to 4 cups of extra-virgin olive oil. This amount is not as taxing on the wallet if you’re straining and reusing the oil to make several tortillas a week, as many Spaniards do, but using so much oil for a single, somewhat humble meal seemed excessive.
An intensely rich, velvety, melt-in-your-mouth egg-and-potato omelet that didn’t require using a quart of oil.
We first stuck with the traditional volume of olive oil until we could determine the proper type and ratio of ingredients. We found that 1½ pounds of russet potatoes yielded the right size tortilla-perfect for four people as a light dinner. After hours of slicing and dicing, we also found that very thin slices of quartered potatoes produced the best distribution of egg and potato. For the onion, tasters preferred the mellow flavor of standard yellow onions. We also settled on the perfect ratio of eggs to potatoes that allowed the tortilla to set firm and tender, with the eggs and potatoes melding into one another. Traditional recipes call for flipping the tortilla with the help of a single plate when the bottom is set but the top is still liquid. When we tried this, the result was an egg-splattered floor. Then we wondered whether we could trap the heat inside the pan to set the top. We tried placing a lid on the pan as soon as the bottom of the egg-and-potato mixture was set. Two minutes later, the top was cooked just enough to make flipping less risky-but still not easy. In the end, we fudged tradition: We slid the tortilla out of the pan and onto one plate. Then, placing another plate upside-down over the tortilla, we easily flipped the whole thing and slid the tortilla back in the pan, making a once-messy task foolproof.
With those issues settled, we started to scale back on the oil, but ran into different problems, from unevenly cooked potatoes to mushiness. With more oil, it was easy to cook a large volume of potatoes without disturbing them. The problem was that with less oil, the potatoes were half frying, half steaming. Then we realized we had made our potato choice of russets while we were still using the traditional cooking method. With less oil, did russets still make sense? We started a new tortilla, this time with slightly firmer, less starchy Yukon Golds. With less oil in the skillet, they were a winner: starchy enough to become meltingly tender as they cooked, but sturdy enough to stir and flip halfway through cooking with fewer breaks. In fact, the new approach worked so well that we reduced the oil to a mere 6 tablespoons. The rich flavor was still present as long as we used high-quality extra-virgin olive oil, a much more appealing prospect since we were now using only a moderate amount. And while the tortillas were perfectly good plain, we prepared two additional tortillas with typical additions (roasted red peppers and peas, and Spanish chorizo sausage) and served them with a batch of garlicky mayonnaise.