Preparation : Mash potatoes with butter, salt, and milk. Prepare filling. Fry meat with seasonings. Add onions. Add pine nuts and mushrooms. Fry well. Spread 1/2 of potato mixture in bottom of greased pan. Spread filling over. Cover with remaining potatoes. Dot with butter. Sprinkle with bread crumbs. Bake at 250 degrees for 25 minutes. Cut in squares to serve.