1 Peel and slice the potatoes and rinse them thoroughly.
2 Add the oil and a knob of butter to a frying pan and cook the potatoes.
3 Dice the onions and mince the garlic, then brown them in a little butter or oil with the sugar, salt and pepper, until caramelized.
4 Combine both elements and add the chopped parsley, then adjust the seasoning.
5 Beat the eggs well, then add the potatoes.
6 Cook the tortilla in a frying pan in a little butter or oil like you would with an omelet, mixing from time to time then leaving to brown.
7 Flip the tortilla using a plate and cook on the other side.
8 Once both sides are browned, remove the tortilla from the pan and eat hot or cold with a slice of ham.