Vegetable Stuffed Portobello Mushrooms

Name: Vegetable-Stuffed Portobello Mushrooms
Ingredients: 1 cup balsamic vinegar; 1/2 teaspoon garlic powder; 1/2 teaspoon onion powder; 4 large portobello mushrooms, wiped clean and stems removed; 2 tablespoons olive oil; 1 small eggplant, peeled and diced; 1 cup frozen spinach; 1/2 cup shredded mozzarella cheese; 2 plum tomatoes, diced; 1 (6 ounce) jar artichoke hearts in brine, drained and chopped; 1/4 cup grated Parmesan cheese