To confirm doneness, insert a toothpick into the center of a muffin; it should come out clean with no visible batter. Enhance texture and flavor by folding in 1/2 cup of chopped nuts such as walnuts or pecans. For variety, substitute different types of chocolate—milk, dark, or white—or replace chips with raisins or omit entirely. A dash of cinnamon (1/2 tsp) adds a seasonal touch, especially in autumn. To make a loaf instead, refer to a Chocolate Chip Banana Bread recipe. Ripe bananas are essential for a smooth batter; underripe ones will be difficult to mash. To ripen quickly, bake unpeeled bananas on a sheet at 350°F for 10 minutes, then allow to cool before using. Muffins can be stored in an airtight container for 5–7 days or frozen for up to 3 months.