1. Preheat oven to 200 C / Gas 6.
2. Saute the onion and garlic in the olive oil until golden in colour. Add the mince and fry for 12 mins. Next add the peppers and mushrooms and fry for around 6 mins or until soft.
3. Add the tomatoes, oregano, salt and pepper and leave to simmer. In a large greased ovenproof dish, layer a third of the mix and cover with pasta sheets, then pour a third of the white sauce over. repeat for 2 more layers. On the third layer sprinkle the grated cheese over the last layer of white sauce.
4. Bake in the oven for 30 minutes.
5. Slice and Serve with a salad or wedges.