In Spain, a tortilla refers to a baked egg dish similar to an Italian frittata, traditionally made with potatoes. A Spanish tortilla is a perfect summer lunch or dinner dish - delicious served warm, cold, or at room temperature, or chill and cut into bite-sized squares to serve at a party. As with a frittata, feel free to add other cooked vegetables, fresh or dry herbs, or leftovers to your tortilla.
In a large, heavy, ovenproof skillet (cast iron is ideal), heat a generous drizzle of oil over medium-high heat and cook the onion for 4-5 minutes, until starting to turn golden.
Add the sausage and if it’s fresh, cook until the meat is no longer pink, breaking it up with a spoon.
Add the potatoes, and cook, stirring often, for 1-2 minutes, then cover and cook, stirring occasionally, for about 10 minutes, or until the potatoes are tender.
Meanwhile, preheat the oven to 375˚F and whisk together the eggs, half & half, salt and cheddar.
Pour the egg mixture over the potatoes (they will poke through) and continue to cook on the stovetop, running a spatula around the edge to allow the egg to run underneath as it sets.
When the edge is set but the middle is still uncooked, slide the pan into the oven and cook for 10-15 minutes, until set.
Serve in wedges - warm, at room temperature or cold.