Beat the eggs into a bowl with a fork or a whisk, add salt, pepper and Parmesan cheese.
Cook your spaghetti in abundant boiling water.
Drain and pour them in the bowl with the egg mixture. Mix well.
Place the pastry rings into a hot pan containing the oil. Fill the bottom half of the pastry ring with spaghetti (the bottom of the ring is the size of the desired "bun". Depending on how thick you want your pasta buns to be, you can fill it up to the edge. After a first try I decided not to fill the whole ring like otherwise shown in the pic above).
Fry a few minutes. With the help of a lid or plate, flip the frittata and let it cook for a few minutes on the other side.
Build your hamburger now. Place your favorite patty on the bottom bun and top with your favorite ingredients/sauce. Place your top pasta bun and serve with fries or a salad.