Make the tomato sauce: pour a little olive oil into the cooking pot and let the onion cube and the garlic cubes simmer in it. Add the tomato cube and season with salt and pepper. Cook for 30 minutes. At the end of the cooking time, add the basil and oregano. Set aside.
Allow the grilled aubergine slices to thaw completely in a little olive oil, let the grill mix and vegetable mixture simmer gently, season with salt and pepper.
Build the lasagna in an oven dish. A layer of tomato sauce, a layer of grilled aubergine slices, a layer of grill mix vegetables, a layer of grilled aubergine slices. Continue like this until desired number of layers, finish with a layer of tomato sauce and mozzarella slices.
Bake in the oven at 180 ° C for 30 minutes to obtain a beautifully gratinated top surface.