Trim ends of zucchini; place in a steamer basket. In a saucepan, bring 1 in. of water to a boil; add basket. Cover and steam for 5 minutes. When zucchini is cool enough to handle, cut in half lengthwise; scoop out pulp, leaving a 1/4-in. shell. Set pulp aside in a bowl.
Clean mushrooms with damp towel and trim stems, chop coarsely. Melt butter in large non-stick skillet sauté onions until translucent, add garlic, chopped mushrooms and sauté for about 1-2 minutes until all tender. Add bread crumbs,1/3 cup parmesan cheese and seasoning, when all ingredients are well incorporated remove from stove.
Toss with Zucchini pulp gently, Stuff Zucchini boats with this mixture and arrange them in baking dish. Sprinkle a little grated parmesan cheese over the tops. Bake at 350 degrees for about 15-20 minutes until filling is just bubbling and cheese is melted on top. Cool slightly, serve.
Note: Its important to trim stems they will be tough and make filling woody.
Make sure you do not burn garlic or it will bitter the filling.
This can be served as an appetizer cut in 2-inch slices, served over Noodles toss with a light lemon olive oil or white rice.
These can be done a day before, and stored in Refrigerator overnight, and then put in Oven before serving.