For the sauce
Preheat the oven to 180°C/350°F/Gas mark 4. Grease a 33 x 23cm/13 x 9in tin with a little vegetable oil.
To make the sauce, heat the olive oil in a large heavy saucepan. Add the garlic and sauté until the garlic begins to brown. Remove the garlic from the oil with a slotted spoon; discard. Add the onion to the garlicinfused oil and sauté lightly.
Add the tomatoes and mushrooms, and cook over a medium heat for about 30 minutes. Add the basil, oregano and parsley, and bring to a boil. Remove from the heat and stir in the Parmesan. Put aside.
Cook the pasta in a pan of salted boiling water for 8–10 minutes until aldente, then drain thoroughly.
Combine the spinach, egg white, cottage cheese, mozzarella, onion, garlic, parsley and broccoli in a bowl. Blend well.
Stuff the shells with the cheese mixture, using about 2 tablespoons for each shell. Arrange in the prepared tin. Pour the sauce over the shells,. bake in the oven for 30–40 minutes. Serve hot.