Pasta dishes are always a good idea!
Bring salted water to the boil in a saucepan. Add oil and cook the macaroni until al dente. Drain, return to the pot and mix thoroughly with 2 tablespoons of butter. Cover and keep warm.
Sauté the fennel in the remaining butter for 3-4 min. Add the mushrooms and sauté for 2 min. Next, mix in the shrimp and remove the frying pan from the stove. Mix the pepper, pasta, shrimp mixture and béchamel sauce.
Form the mixture in a greased gratin dish and sprinkle with parmesan. Spread the tomato slices around the edge, brush with olive oil and sprinkle with oregano.
Bake the casserole at 180 °C in a heated oven for about 25 minutes until golden brown and then serve hot.