1. Preheat the oven to 180 C. Grease a 1.5 litre (6 cup) ovenproof dish.
  2. Heat half of the olive oil in a frying pan and cook the zucchini on a low heat for 5 minutes until starting to soften. Add the garlic and cook for 1 – 2 minutes. Add the nutmeg, salt and pepper to taste, then transfer to the prepared dish.
  3. Heat the rest of the oil in the pan and cook the onion until soft, about 15 minutes. Add the tomatoes, verjuice and bay leaves, and cook until the sauce is thick and the liquid is almost evaporated, stirring regularly. Season well and remove the bay leaves.
  4. Sprinkle the gruyere cheese on the zucchini, then spread the tomato sauce on top. Mix the breadcrumbs and parmesan together, sprinkle over the sauce and drizzle with olive oil. Bake for 25 minutes or until golden.