1. Bring a large amount of salted water to a boil in a cauldron. Add 2 tbsp of extra virgin olive oil and the cannellonis. When they are cooked, drain them and lay them out separately on a kitchen cloth. Preheat the oven to 350°F.
2. To prepare the filling: Peel the onion and the clove of garlic; chop them, then sauté them in a cauldron with extra virgin olive oil until golden brown. Add the sausage in pieces and the ground beef; cook with salt and pepper.
3. Add the chopped rosemary, sage, and white wine; let the liquid evaporate over medium heat. Sprinkle with flour, mix again, then add the heavy cream and continue cooking for 10 minutes, stirring with a wooden spoon.
4. Turn off the heat, blend the preparation, then pour it into a bowl. Add the eggs and parmesan, and mix again, then let it cool down.
5. With a spoon, fill the cannellonis and arrange them on a lightly oiled baking dish.
6. To prepare the sauce: Chop the onion. Sauté it in a saucepan with oil until it is translucent. Add the tomatoes, salt, and pepper, and let it reduce for 15 minutes. Add the chopped basil.
7. Cover the cannellonis with the sauce, sprinkle with mozzarella, and bake for 20 minutes. Serve in the baking dish.