Brown the beef mince in a pan, without using oil.
Once it is brown all over, stir in the onion, red pepper and green pepper.
Add the dried oregano and the dried rosemary, the tin of chopped tomatoes and four tablespoons of tomato purée and mix well.
Put one third of the mixture in the base of the oiled slow cooker pot.
Top with three sheets of lasagne, broken to fit.
Put another third of the mince mixture on top of the lasagne sheets, and top again with three lasagne sheets, broken to fit.
Repeat once more to use up all of the mince mixture.
Mix the reduced fat creme fraiche, grated mozzarella and a splash of milk in a small bowl. Pour it over the top layer of pasta and spread it around to cover the top. Add a few leaves of fresh basil.
Cook on low for 5-6 hours.