Heat oil in skillet and add the diced potatoes. Cook until tender. (There's no need to peel them.)
In a separate skillet cook the chorizo until it is cooked thoroughly and then add the eggs to the skillet.
Once the eggs have been scrambled in with the chorizo add the potatoes to the skillet and mix all three together with salt and pepper.
Sprinkle the chopped onions on the top and serve warm.
Optional: garnish with cheese and salsa