Preheat oven to 180 C / Gas 4. Bring a large pot of lightly salted water to the boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.
Place minced beef in a large, deep frying pan. Cook over medium high heat until evenly brown and crumbled. Drain excess fat and set aside.
Heat oil in a large heavy frying pan over medium heat. Saute onion until soft and translucent. Stir in garlic, and cook for 30 seconds. Add cooked beef, tomatoes, pasta sauce and mushrooms; bring to the boil. Reduce heat, and simmer 20 minutes.
In a baking dish, layer 1/2 of the pasta, 1/2 of the meat sauce, 1/2 of the soured cream and 1/2 of the grated cheese. Repeat layers.