Saute chorizo in a heavy skillet over moderate heat, breaking it up with a wooden spoon, until browned, about 5 minutes. Add the green onions and garlic and cook for about 2 minutes.

Whisk together the eggs, water, salt, and pepper and add to the skillet. Cook, stirring frequently, until light and fluffy, 3 to 4 minutes.

Add the cheese and cilantro and stir until the cheese is melted, about 1 minute.

If using Mexican Crema or sour cream, top each serving with a small dollop.