Poach baby marrows, aubergines and onions whole for 1 minute in boiling salted water. Cut tops off tomatoes, aubergines, marrows and onions. Scoop out interiors of vegetables and keep pulp of aubergines and marrows for stuffing.
Sauté meats and onion in olive oil. Mix other ingredients in a bowl and then add them to the meat and onion mixture. Add pepper and salt, to taste. Sauté for a few minutes, stirring continuously, and then stuff scooped-out vegetables with the mixture.
Place stuffed vegetables in an oven-proof baking dish to which you have added a little olive oil; place a knob of butter on each vegetable and bake in a moderate