Cut the zucchinis in half and hollow them out. Make a filling with the chopped onions, veal, mushrooms, and chopped parsley. Add a bit of water to the beef concentrate and mix it with the filling. Fill the zucchinis with this mixture. Cook the zucchinis in a buttered pot with the white wine. In a baking dish, make a layer of cooked noodles and place the zucchinis on top. Sprinkle with parmesan, drizzle with melted butter, and bake until golden brown.