Wash the potatoes and cook in boiling water for about 20 minutes. Drain the potatoes, rinse briefly in cold water, peel and let them cool down.
Peel and finely dice the onions. Quarter the chorizo slices. Cut potatoes into slices. Heat 2 tablespoons of oil in a pan (approx. 24 cm Ø). Fry half of the onions and the potatoes for about 10 minutes at medium heat. Season with salt and pepper.
Add half of the chorizo and fry for 4-5 minutes more. Whisk the eggs and season with salt and pepper. Add half of the eggs to the pan and let them fry for 7-10 minutes. Make tortilla using a plate and fry for another 5 minutes. Fry another tortilla of the remaining ingredients.