First off, to make olive oil, you gather the olives from their trees, either manually, using tiny rakes (the traditional method), or with an automated harvester (the modern method). The amount of time it takes from harvest to press is important - the less time the better, as more flavor is retained in the olive. Modern methods for harvesting are an improvement in this respect.
After harvesting, the olives are ground into a pulp. Traditionally, olives were ground using big granite wheels. Unfortunately, it is hard to control the temperature due to friction of these wheels, and they tend to become very hot. This in turn causes the olives to lose flavor and health components. Nowadays, olives are ground using more gentle techniques, allowing for greater temperature control. An oil is classified by the IOOC as 'cold pressed' if the fruit pup stays below 27ºC during the grinding stage.
Using the traditional method, the pulp is spread in between discs, layered on top of each other. A hydraulic press then squeezes out the oil. At this point high quality oil should habe a nice golden color. The modern method spins the pulp in a centrifuge, where the oil passes out through a fine mesh. Nowadays, this is how most olive oil is made.
I know myself, I've been caught at the grocers, staring confusedly at the different types of oils on the shelf. A quick rule of thumb, if the oil is labelled 'virgin' or 'extra virgin', they are going to be the highest quality, with the most intense flavor. Virgin basically means that the oil was produced using physical means and no chemical treatment. They are pure and delicious, and thus, more expensive. The only differences between extra and virgin are there grade - extra virgin has superior taste, while virgin has good taste.
Refined olive oil, on the other hand, is virgin oil that has been further processed using charcoal, filters, and/or chemicals, and subsequently, some of the flavors and/or health benefits are lost. Refining may be performed because and an oil has slight defects and/or a high acidity, preventing it from being labelled as 'virgin' - these defects can be corrected by refining. Refined oil can also be made from low quality or overripe olives. If the label on the bottles states 'pure olive oil' or 'olive oil', it means that it is a blend of oils, usually refined and virgin. Most olive oils that are on the grocery store shelf fall into this category, as well as 'light' and 'extra light', which are just more refined oils, hence the lighter color. This does not meen that they have fewer calories.
After spending a few hours researching olive oil's smoke point, the point at which fat breaks down, gives off an odor, and starts to smoke, I've realized that this is a hot topic with a lot of conflicting views. Personally, I love the taste of olive oil, and its health properties, therefore it's a big part of my diet. But, I would hate to think that there is the possibility of ruining any of these components by heating the oil too high, especially since my stove is so variable. I have found various numbers quoted for the smoke point of extra-virgin olive oil, ranging from 375 - 410 ºF, which is far higher than we normally use for light frying. Honestly, if I'm going to make a stir fry, or lightly fry some veggies, I will definitely use olive oil, but I am way too terrified to use my precious oil for deep frying. It would be a shame to accidentally burn all of that deliciously expensive oil at a temperature that I feel is sometimes hard to regulate. Just last week, I accidentally heated 3 cups of vegetable oil too high and it started to smoke. Such a waste.
If you want to use olive oil to sauté the onions and potatoes in this recipe, and anything else for that matter, it shouldn't be an issue, and because the flavors from the oil absorb into the potatoes and onions, you are better off using a nice tasting oil. (In my opinion, a good olive is worth having around. It's wise to check out an Italian grocer, or deli. They tend to have a more reliable selection.) I like to use Partanna's extra-virgin olive oil . I am completed obsessed with the flavor. I buy it in huge tins from amazon.
I've seen tortilla de patatas served with sofrito, a Spanish tomato sauce, but lately I've had a real craving for Marcella Mazan's rich buttery tomato sauce. I had a little for dinner, and then some more for breakfast. I love that about this dish - perfect for any meal.
TORTILLA DE PATATAS RECIPE (print)
makes one 12 inch tortilla cut into 8 pieces
notes: I chose to cut the potatoes into tiny cubes, but I have also made the tortilla using thinly sliced potatoes - 1/8 inch on the mandoline. I used butter to fry the potatoes and onion because I prefer the flavor, but typically olive oil is used.
1/2 cup butter (roughly), salted or unsalted
1 sweet onion, diced
3 - 4 small potatoes (Yukon gold or red) - something low in starch
1 tsp salt
1 - 2 oz Parmesan cheese, grated
In a large frying pan, on low heat, saute the diced onion in 2 tbsp of butter, until they have become soft and translucent. Remove from the pan and set to the side.
In the same pan, add 1/4 cup of butter and the diced potatoes. Fry on low-medium heat until they have become soft and begin to turn light brown. Remove from the pan and set to the side.
In a large bowl, lightly beat the eggs. Add the onions and potatoes, salt and pepper, and the grated Parmesan cheese. Stir. Let the mixture sit for 10 minutes.
Place a 10 - 12 inch frying pan on low heat. If the frying pan is non-stick, add one tbsp of butter. If you are working with a cast iron pan, you made need to use more butter, 2 tbsp or so. Once the butter begins to sizzle, add the egg mixture and flatten it out with a spatula.
Place a lid over the frying pan, and cook for 5 - 10 minutes, or until the bottom has browned - noting that the egg in the center will still be runny and wet when you are ready to flip. Run the spatula around the side of the frying pan to make sure that the tortilla lifts easily from the pan. Suit up with some oven mitts. Place a 12 inch plate upside down on top of the frying pan. Place one hand on the plate and one hand on the frying pan handle. Gently turn the frying pan over and the tortilla will fall onto the plate. Slide the tortilla back into the frying pan and continue to cook for 3 - 4 minutes. Turn off the heat and let the tortilla sit for 2 minutes.
Slide the tortilla onto a plate, I usually place whichever side is prettiest and/or less brown, face up. Cut the tortilla into 8 pie shaped slices. Serve with a generous serving of butter tomato sauce, and garnish with fresh arugula.
The tortilla may be stored in the fridge for up to a week, and reheated before serving.
MARCELLA HAZAN'S BUTTER TOMATO SAUCE RECIPE (print)
makes 1 1/2 cups
recipe from the Essentials of Classic Italian Cooking
1 can (28 oz) of whole tomatoes, with juice
1 yellow onion, peeled and cut in half
5 tbsp butter, salted or unsalted
salt to taste
In a medium saucepan, combine the tomatoes plus their juice, butter, and onion, making sure that the onion is submerged in the tomatoes. Bring to a low boil, then simmer for one hour.
Occasionally, give the sauce a stir, trying to crush the large tomatoes against the side of the pot with a wooden spoon.
After an hour, the sauce will have become thick, and the onion soft and falling apart. At this point, the sauce is done. Remove the onion with a slotted spoon and discard. Add salt to taste. Store in the fridge for up to a week, or in the freezer for 6 months.