Cook the potatoes in boiling salted water 10 minutes. Drain and reserve.
Fry the chorizo in a large nonstick skillet until browned. Drain off any excess oil. Add the onion and cook 2 to 3 minutes. Add the potatoes and cook until well-browned, about 10 minutes.
Beat the eggs until frothy and add to the chorizo. Stir with a fork to scramble until soft, not browned. Stir in the cilantro just before the eggs set. Garnish with scallions and cheese and serve.
c.1996, M.S. Milliken & S. Feniger, all rights reserved