Heat 2 teaspoons of oil in a frying pan over mild heat. Add onion and cook for 3 to 4 minutes stirring until the mixture becomes translucent. Add potatoes, thyme and paprika and go on cooking for 2 additional minutes.
Whisk eggs and egg whites in a large basin. Stir the potatoes into the eggs together with cheese, spinach, salt and pepper. Clean the pan wiping. Add 1 teaspoon of oil and heat over mild heat. Pour in the egg mixture, cover and prepare for 4 to 5 minutes until the edges are set and the bottom is browned.
Flip the tortilla inverting a large plate over the pan and turn the tortilla out onto it. Glide the tortilla back into the pan and go on cooking for 3 to 6 minutes.