Spanish potato and onion tortilla

Using a mandolin, thinly slice 3 peeled Yukon Gold potatoes, then pat well with paper towels and lightly salt. Heat ¼ cup (you can use less) olive oil in a large, heavy skillet, then add the potato slices. When partially cooked, add 1 sliced onion and let cook (stirring occasionally) until soft. Remove from pan into a strainer to drain. Separately, lightly mix 6 eggs with 2 Tbsp chicken stock. Add the drained potatoes and onions to the egg mixture. Pour about 5 Tbsp olive oil into another skillet, heat until almost smoking, then carefully pour potato-egg mixture, smoothing out so that its height is even. Run a heat-proof spatula along the sides and center of the pan, letting egg liquid pour into the pan. When omelette is almost cooked, turn off heat and then place a large plate on the pan and flip over. Slide the omelette (wet side down) back into the pan, then cook on low heat until a toothpick comes out clean. This recipe is from The New Spanish Table by Anya von Bremzen. (May 2014)