2 pounds medium Yukon Gold potatoes
1 1/2 pounds fresh chorizo, casings removed (see Note)
1 large onion, finely chopped
2 tablespoons extra-virgin olive oil
Salt and freshly ground pepper
8 large eggs
Toast and hot sauce, for serving
Preheat the oven to 375°. Put the potatoes in a large saucepan and cover with cold water. Bring to a boil and cook over moderate heat until tender, about 25 minutes; drain and let cool. Peel the potatoes and cut them into 3/4-inch pieces.
Meanwhile, heat a 12-inch cast-iron skillet. Add the chorizo, break it into chunks with a wooden spoon and cook over moderate heat, turning, until cooked through and lightly browned, about 8 minutes. Add the onion and cook, stirring, until softened, about 5 minutes. Scrape the chorizo mixture into a bowl and wipe out the skillet.
Heat the oil in the skillet. Add the potatoes, season with salt and pepper and cook over moderate heat, turning occasionally, until golden and crispy, about 6 minutes. Stir in the chorizo mixture. Remove the skillet from the heat.
Using a ladle, make 8 indentations in the potato-chorizo mixture about 1 inch apart; crack an egg into each one. Bake the skillet in the middle of the oven for about 12 minutes, or until the egg whites are just set but the yolks are still runny. Serve at once with toast and hot sauce.
The potatoes can be boiled a day ahead and refrigerated.