For the cheese casserole, preheat oven to 180°C top and bottom heat. Chop onion and sauté in olive oil for 2-3 minutes.
Spread cream cheese on toast and season with salt, pepper and chili. Cut the slices diagonally twice and place half of the triangles side by side in a baking dish. Spread half of the sauteed onions and half of the grated gouda on top of each.
Layer a second layer in exactly the same way. Whisk the milk well with the egg and spices and pour over the bread. Leave to stand for 5 minutes.
Bake the cheese casserole for 40 minutes until golden brown. Sprinkle with parsley and serve with fresh tomatoes.