Boil the milk and the butter in a casserole.
Add the corn flour, the salt and pepper.
Add the parmesan cheese, egg and chopped walnuts. Stir until it comes off from the edges.
Spread on a baking paper and let cool down.
Cut circles about 8 cm in diameter.
Fry them in a frying pan until they become brown on the surface.
In a casserole sauté the onions in olive oil, vinegar and brown sugar. Keep it on low heat for 20 minutes.
Place the cakes on plates and place a spoon full of onions on each cake.
Decorate with the cheese on top. Heat up in a frying pan with a lid until the cheese melts.