Heat the oil in a medium pan on medium heat for 1-2 minutes. Finely chop the onions and potatoes then add to the pan and sauté on medium-low for about 8 minutes or until the onions are translucent and the potatoes are fork tender.Whisk the eggs with the Parmesan and saffron in a medium size bowl then add to the frying pan. Cook for about 5 minutes, stirring continuously to scramble. Remove the eggs from the pan and set aside in a medium bowl. Return the frying pan to the burner and add another 1-2 tbs. of olive oil. Increase the temperature to medium-high and heat the oil for 1 minute. Return the eggs to the pan, forming a patty with a spatula as they cook, shaking the frying pan gently to prevent the eggs from sticking and pressing down to ensure the frittata is uniform.Cook for about 2 minutes then cover the frying pan with a large flat plate. Hold the handle of the frying pan and press down on the center of the plate with the palm of your other hand then flip the frittata onto the plate. Slide the frittata back into the frying pan and cook for another 2 minutes on the other side. Set aside to cool for a few minutes then cut into desired pieces. Consume with 4 days of preparation.