In a deep pan, fry the grated carrots, chopped onions, sliced garlic and mushrooms in some oil, and add water. When soft, add the mince and fry until it becomes crumby. Add the tomatoes and season with salt, a pinch of sugar, pepper, basil and oregano. Let the mixture simmer until slightly thickened.
In another dish, to prepare the sauce, melt the butter and fry the flour until browned, and while stirring continuously, add the warm milk. Stir until the sauce thickens and becomes homogeneous, season with a little salt and pepper, if desired, add a little grated cheese and remove it from the fire.
In a greased baking tray, put a layer of lasagna sheets, then tomato sauce and béchamel sauce, repeat and finish off with lasagna sheets, topped with slices of fresh tomatoes and poured with plenty of béchamel. Sprinkle the top with grated cheese, cover the tray with foil and bake it in a preheated oven at 428°F (220 °C) for about 30 minutes.
Then remove the foil and return the dish to the oven for 10 minutes, or until the cheese is browned. Leave it to cool to set. Enjoy!