For the sauce
1. Peel and finely chop the onion and garlic.
2. Clean and chop the mushrooms.
3. Heat the oil and sweat the onion and garlic until translucent.
4. Add the mushrooms and mince and break up the mince to brown right through.
5. Add and chop the tomatoes and simmer for 10 minutes.
6. Season with salt, pepper and herbs.
For the béchamel
1. Melt the butter in a pan, stir in the flour and sweat briefly.
2. Whisk in the milk, season with salt, pepper and nutmeg and cook gently over a low heat for 15 minutes, stirring occasionally.
3. Heat the oven to 180°C.
4. Grease the baking dish and fill with alternate layers of mince and tomato sauce, cheese and lasagne, finishing with béchamel sauce and cheese.
5. Bake the lasagne in the preheated oven for 40-45 minutes until lightly browned on top.