The day before serving, prepare "cheese" from yogurt by mixing yogurt with 1/2 teaspoon salt and placing it in a strainer lined with several layers of cheesecloth. Squeeze cloth very gently around yogurt and place over bowl. Refrigerate and drain for at least 10 hours. Before continuing with recipe, carefully remove cheesecloth from ball of cheese. Stir polenta into boiling water. Add 1/2 teaspoon salt. Cover and cook over low heat, stirring frequently, for 15 minutes or until thick and soft. Pour into a 9-inch nonstick pie plate and spread evenly over bottom and sides. Preheat oven to 425 F. Spread pizza sauce over polenta. Arrange vegetables over sauce, top with yogurt cheese, capers and Parmesan cheese. Bake 25 minutes or until pie is bubbling hot throughout. Remove from oven and top with basil.