Chop onion and sweet pepper, sautee in vegetable oil for several minutes. Add ground meat, sautee well through. Add chopped mushrooms and simmer the mass until soft. Add tomato puree, Worcestershire sauce and stock. Season the mix with salt, ground pepper, basil and bring to simmering, reduce heat and poach over low heat for 20 minutes.

Bring enough water to cook potatoes in a pan to boil, add salt, plunge peeled potatoes and boil for 20 minutes, until done. Drain water and mash potato, add butter and hot milk. Beat the mass up until airy.

In an ovenproof baking pan put meat mix, space it evenly, put potato mass and space it with a fork, shaping slight waves on the surface.

Place the pan in preheated oven and bake until gold crust appears on the surface. Serve the casserole hot.