Roasted Polenta with Garden Vegetables

Name: Roasted Polenta with Garden Vegetables
Ingredients: 4 cups chicken stock; 4 tablespoons butter; 2 teaspoons ground black pepper; 1 tablespoon salt; 2 cups polenta or cornmeal; 1/2 cup grated Parmesan; 1/2 cup finely shredded basil leaves; Softened butter for the pan; Olive oil, as needed; 1/4 cup balsamic vinegar; 1 clove garlic, minced; 3/4 cup olive oil; Salt and pepper; 2 red onions, cut into 1/2-inch thick slices; 2 zucchini, cut into 1/2-inch thick slices on the diagonal; 2 yellow squash, cut into 1/2-inch thick slices on the diagonal; 2 red bell peppers, cored, seeded, and cut into 2-inch pieces; 1/2 pound asparagus, tough ends removed; 1/2 pound mushrooms