In a large skillet, saute the mushrooms, pepper and onion in 2 teaspoons oil until almost tender. Add the eggplant, zucchini, tomatoes, garlic, Italian seasoning and salt. Saute for 8-10 minutes or until vegetables are tender., In another skillet, cook polenta slices in remaining oil over medium-high heat for 3-4 minutes on each side or until lightly browned. Serve with ratatouille; sprinkle with cheese if desired.