First cut the onion into fine cubes and sauté with a little oil. Then add the tomatoes and season the tomato sauce with vegetable stock, salt and pepper to taste. Let it simmer for 10 minutes.
Place 1 slice of ham and 2 slices of Gouda cheese on each chard leaf. Now roll up and secure with a wooden stick. Fry the chard rolls over medium heat with a little oil in a pan. Be careful not to get too dark. Finally pour the tomato sauce over it and rub some parmesan over it.