For the béchamel, melt the fat in a saucepan, stir in the flour and sauté over a low heat for about 5 minutes. Add milk and stock while stirring. Wash the rosemary, thyme and bay leaf, dab dry and add, except for something to garnish.
Simmer for about 15 minutes at low heat, stirring occasionally. Meanwhile clean, wash and cut the peppers into narrow strips. Wash and clean the zucchini and cut them into approx. 5 mm thick slices.
Clean and quarter the mushrooms. Heat oil in a pan and fry vegetables and mushrooms. Season with salt and pepper. Remove and put aside. Season béchamel with salt, nutmeg and cayenne pepper and remove the herbs.
Peel and halve the garlic and grate it in an ovenproof casserole dish (approx. 20x25 cm; 1 1/2 litres capacity). Put some béchamel in the dish and put 3-4 lasagne plates in it. Layer béchamel, vegetables and the rest of the lasagne sheets one after the other.
Finish with béchamel and vegetables and garnish with herbs. Grate the parmesan finely and mix with breadcrumbs. Sprinkle the lasagne with it and bake in a preheated oven (electric: 175 °C/ gas: level 2) for 45-50 minutes on the 2nd rung of the oven.
Bake the splint from below until golden brown. Serve with a green salad.