Preparation Combine 6 cups water, oil and salt in heavy large saucepan. Bring to boil. Gradually whisk in cornmeal. Reduce heat to low; cook until polenta is very thick, stirring occasionally, about 30 minutes. Stir in 1 1/4 cups Parmesan cheese and butter. Ladle polenta into shallow bowls. Top with Porcini Mushroom Sauce. Serve with additional cheese, if desired.