For the tomato sauce, sauté the onion and garlic in olive oil without letting the ingredients take their color. Add the tomatoes and bay leaf and simmer for 20 minutes.
Season to taste with salt, pepper and a little sugar. Remove the bay leaf. Put the sauce in a baking dish. Halve the peppers lengthways. Remove the dividers and cores.
For the filling, mix the minced lamb with the egg, breadcrumbs, harissa and garlic. Sauté the onion and parsley in a little olive oil and add to the mince mixture. Season with salt and pepper and pour into the halved paprika. Place the filled halves on top of the tomato sauce in the pan. Bake in the oven preheated to 180 degrees for 35-40 minutes.