Prepare the Zucchini:

1. Bring a large pot of salted water to a boil. Set up an oven rack over a kitchen towel (you will need this to cool the blanched zucchini).
2. In the meantime, carefully halve the zucchini lengthwise - this works best with a long knife. Scoop out the flesh, chop it roughly and set it aside. Make sure you leave the zucchini walls at about 1/4 of an inch, so there’s enough room for the filling but they still keep their shape.
3. Once the water is boiling, add the zucchini halves and cook them for one minute.
4. Drain them immediately and place them, cut side down, on the oven rack.

Make the Filling:

1. Heat the oil in a large pot over medium-high heat. Add the sausage and brown it for 5 minutes, stirring frequently.
2. Add the onion and garlic and continue cooking for 5 minutes. Then add the chopped zucchini flesh and cook for about 10 minutes, or until it doesn’t look watery anymore. (This depends on your zucchini - especially ones on the larger side will have more water in them.)
3. Once everything is starting to look nicely browned, stir in the tomato paste. Roast it for a minute, stirring constantly. Pour in the red wine (or stock; careful, this might splatter!), stir in the tomatoes and season with Italian herbs, salt and pepper.
4. Cook on medium-low heat for 10-15 minutes or until the sauce has a nice thick consistency.
5. Check for seasoning and add more salt or pepper if needed.

Finish the Dish:

1. Preheat the oven to 400°F.
2. Arrange the blanched zucchini halves in a lightly greased 9x13 inch baking dish.
3. Spoon the filling into the zucchini. It might seem like too much - but you can really stuff it all in there.
4. Sprinkle the stuffed zucchini with parmesan cheese and mozzarella, then bake on the middle rack for 20-25 minutes, or until the cheese is bubbly and starting to brown.