Cook the pasta with water and oil in a big pot on high heat for 10 minutes. Stirring constantly
In the first pan: Put the oil in the pan until it boils a little and then put the onions and stir well for three to five minutes and then add mushrooms, ground beef, salt and pepper and stir the contents for ten minutes
For the bechamel sauce: Put the butter, milk and flour in another pan and stir for 10 minutes
Place the pasta in the tray and above it the contents of the first pan and then the bechamel mixture. Put it in the oven for 15 minutes.