Divide the batter among the 12 cups, filling each cup 2/3 full, and bake in a preheated 350 F oven about 20 to 25 minutes, or until a cake tester or toothpick inserted into the middle of a muffin comes out clean. Cool the muffins on a wire rack. These muffins will keep, if well wrapped, at room temperature for three days and refrigerated for up to a week. To freeze, cool completely and then store in an airtight freezer bag. Defrost, covered, at room temperature.