To prepare filling & bake cheesecake: Puree cottage cheese in a food processor until very smooth, scraping down the sides of the workbowl once or twice. Add cream cheese, sugar and 3 tablespoons cornstarch; process until smooth. Add egg, egg whites, sour cream, vanilla and salt; blend well. Measure 3 1/2 cups of the batter into a separate bowl; stir in lemon juice. To the remaining filling, add pumpkin, brown sugar, molasses, cinnamon, ginger, nutmeg, cloves and the remaining 1 tablespoon cornstarch; blend well.