1 Heat the oil in a pan and sweat the shallot and garlic until translucent. Dust with flour and cook briefly. Stir in the tomato puree and then the red wine and stir until smooth. Add the tomatoes, carrots, oregano and thyme.
2 Clean the mushrooms and cut into pieces. Add to the pan. Simmer gently for 10-15 minutes and season to taste with salt and pepper. Stir in the Parmesan.
3 Wash and sort the spinach and blanch briefly in boiling, salted water. Drain, refresh in cold water, squeeze out and chop roughly. Mix the spinach with the ricotta, 200 g of grated mozzarella, egg yolks, cornflour, a little nutmeg, salt and pepper. Check the seasoning.
4 Grease a dish and put a little tomato sauce in the bottom. Spread a layer of lasagne sheets on the tomato sauce, then add half of the spinach mixture and cover with a layer of lasagne. Add another layer of tomato sauce and continue in this way until all the ingredients are used up, finishing with a layer of lasagne.
5 Mix the remaining grated mozzarella and the Gruyere with the crème fraîche, spread on top of the lasagne and bake in an oven preheated to 180°C (160° fan) | 350F | gas 4 for 30-40 minutes.
6 Leave to stand in the dish for 5 minutes, then cut into pieces and serve.