This recipe is adapted from the June 1992 issue of Bon Appetit magazine.
Polenta: Whisk cornmeal and water in small bowl to blend. Bring broth to boil over high heat. Add cornmeal mixture all at once and stir until mixture boils and thickens. Reduce heat, add corn and simmer until very thick (about 15 minutes). Mix in Parmesan cheese. Spoon into ungreased 9" cake pan, smooth top and chill. This can be made a day ahead.
Sauce: Heat oil, add onion and cook until tender (about 3-5 minutes). Add garlic, basil, oregano and red pepper flakes and saute one minute. Increase heat to medium high and add mushrooms - saute 2 minutes, then add white wine and cook until liquid has evaporated. Add tomatoes and bring to a boil. Reduce heat and simmer until reduced, about 30 minutes. Can be made one day ahead and refrigerated. Polenta should be firm enough to cut into wedges.
To serve:
Preheat broiler. Turn polenta out onto cutting board, tapping pan to release if necessary. Cut into wedges and brush with olive oil. Place oil side down on cookie sheet. Brush top side with olive oil and broil until golden - about 3 mins. Bring sauce back to simmer, place polenta on plates and spoon sauce over. Sprinkle with additional Parmesan. 6 servings.