Bananas add moisture, creaminess and flavor to baked goods, and in certain baked goods, they can substitute for some or all of the butter. For the best taste, reduce the fat, but don't omit it completely. Even a few tablespoons of butter combined with banana puree makes a big difference in the taste and tenderness of your muffins, quick breads or cakes.

You can substitute mashed banana for some or all of the butter in baked goods, but start slowly and use the right ratios. When substituting banana puree, use half to three-fourths the amount of puree as you would butter. For every cup of butter in a recipe, use 1/2 to 3/4 cup of puree. In the beginning, substitute only part of the butter with banana. If you're happy with the results, next time, replace more butter with banana puree.

Banana puree works better in some baked goods than others. Banana puree has a distinct, sweet flavor that will carry over to your baked good. If you don't want a banana-flavored cake, use the puree in rich, highly flavored cakes, such as chocolate, gingerbread or spice cakes. The intense flavors of these cakes mask the banana taste. Try applesauce, which has a neutral flavor, in mild-tasting baked goods. Banana puree performs best in moist, dense muffins, quick breads and cakes. Cookies made with banana puree tend to be puffy and cake-like, rather than chewy or crisp.

The best bananas for baking are those that are extremely ripe. The skins should be dark brown to black, but discard those that are oozing liquid or that have a strong odor. Don't use firm, yellow bananas, which won't provide enough moisture in baked goods. Peel the bananas and mash them with a fork or puree them in a blender or food processor. Use a glass measuring cup to measure banana puree. Freeze extra banana puree in one-cup increments -- or whatever measure you use most frequently. Freeze the puree in heavy plastic freezer bags and store it at 0 degrees for up to three months. To use frozen puree, thaw it in the refrigerator overnight or place it in a bowl and run warm water over it in the sink.

Baked goods made with banana puree may bake faster, especially if you omitted all or most of the butter. Turn the oven temperature down by 25 degrees and reduce the cooking time by 5 to 10 minutes. Remove the baked good from the oven when it springs back lightly to your touch. Avoid overbaking, which will toughen and dry out the baked good.