1. Cut zucchini in half lengthwise. Scoop out insides, leaving shells about 1/4 inch thick. Reserve about half of the insides.
2. Heat 1 Tbsp of olive oil in a skillet on medium high heat. Sauté onion and garlic until soft.
3. Add mushrooms and reserved zucchini insides, and sauté another 2 minutes. Remove from skillet and set aside.
4. In the same skillet heat a Tbsp of olive oil on medium high heat. Add the ground turkey. Lightly brown the turkey, stirring only occasionally. After the turkey browns on one side, stir it so that it has a chance to brown on other sides. Cook until the ground turkey is lightly browned, about 6 minutes.
5. Stir in the reserved onion and mushroom mixture. Add the chicken broth. Stir in tomato, basil and rosemary and cook 1 minute longer. Drain any excess fat. Remove mixture from heat and set it aside.
6. When mixture has cooled, add cheese, egg, salt and pepper. Fill zucchini shells with mixture.
7. Fill a baking pan with 1/4 inch of water. Place filled zucchini halves in pan and bake at 375 degrees for 25-30 minutes, until golden brown. Zucchini should be soft at this point. Remove zucchini from pan and serve while hot.