Combine butter, corn syrup and 1 1/4 cups powdered sugar in large, heavy-duty saucepan. Bring just to a full boil, stirring constantly, over medium-low heat. Remove from heat. Add remaining 1 cup powdered sugar, peppermint extract and 3 to 4 drops of food coloring. Stir vigorously for 2 minutes or until well blended. Pour fondant onto prepared baking sheet; do not spread. Let stand for 4 to 5 minutes or until just cool enough to handle. Do not let fondant cool too much as you will not be able to knead. Lift up edges of fondant with rubber spatula and fold to center to make a mound. Knead for about 2 minutes or until soft. Flatten fondant to roughly a 6 x 4-inch rectangle and place on a piece of plastic wrap. Cover fondant with another piece of plastic wrap. Roll out to roughly 1/8-inch thickness to form a 12 x 8-inch rectangle. To make a more even rectangle, fondant can be trimmed to size. Keep fondant covered with plastic wrap so it will not dry out.