Turn on the oven to preheat to 180 degrees. Boil the pasta in salted water until tender, according to the instructions on the package.
Drain the pasta and transfer back to the saucepan, add 25 g of butter, mix well.
Heat the remaining butter in a saucepan. Pour the fennel into a saucepan, cook for 3-4 minutes. Add mushrooms, cook for a couple of minutes. Then add the shrimps, stir and remove the saucepan from the stove. Put the contents of the skillet in the pasta pot, add the cayenne pepper and béchamel sauce.
Grease a large ovenproof dish with butter, put the pasta and sauce in it, but the tomatoes on top, sprinkle with cheese and oregano. Place the pasta in a preheated oven for 25 minutes. Serve the baked pasta hot.