Banana-Raisin Muffins

Preheat the oven to 375°F (190°C). In a bowl, mash the ripe bananas. In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. In a large mixing bowl, cream the unsalted butter and granulated sugar. Beat in the egg and vanilla extract. Gradually add the mashed bananas and mix well. Alternately add the dry ingredients and milk to the banana mixture, starting and ending with the dry ingredients. Mix until just combined. Fold in the raisins. Spoon the batter into greased or lined muffin tins, filling each about 2/3 full. Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean. Allow the muffins to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.