Cook cassava in salted water until tender but not mushy. Drain and slice.
Thinly slice onions.
Slice chorizo and cook in a pan (you won't need any fat). Reserve.
In the same pan, melt 1 tablespoon ghee or butter. Add onions, cassava and a pinch of salt, and cook in low heat until soft and slightly browned.
Whisk eggs with a pinch of salt (you won't need much because chorizo is usually very salty).
Add another tablespoon of ghee or butter to the pan, let melt, add chorizo, and pour the eggs on top.
Let cook until the eggs have almost set (covering the pan with a lid helps), then carefully use a spatula to make sure the tortilla lifts easily from the pan, and slide it on a large plate or flat pan lid (the side that was on the bottom of the pan should remain on the bottom of the plate/lid).
Quickly and without hesitation, invert the tortilla on the pan so that it cooks on the other side.
When it's done, divide in portions and serve with your choice of vegetables.