Preheat the oven to 200C/400F/Gas mark 6.
Heat the oil in a pan and brown off the mince.
Add the onion, pepper and mushrooms, and cook for another 5 minutes.
Add the chopped tomatoes, beef stock, and tomato puree and simmer for 15 minutes.
Meanwhile, to make the white sauce, melt the butter in a small pan, then stir in the flour to make a roux. Slowly whisk the milk and bring to the boil, whisking continuously, until it is thick and creamy. Add half the cheese and stir to melt.
Layer the mince and lasagne sheets, finishing with lasagne sheets on top.
Pour over the white sauce then sprinkle with the remaining cheese.
Bake in the preheated oven for 45 minutes, until the top is bubbling and golden.
Please note: this recipe has been created and uploaded by a member of the Tesco Real Food online community. Tesco does not test customer recipes so cannot accept responsibility for the content, validate the results or answer queries regarding them.