Preheat Oven: Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or lightly grease the cups.
Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
Mix Wet Ingredients: In a large mixing bowl, mash the bananas until smooth. Add the peanut butter, melted butter, granulated sugar, and brown sugar. Mix until well combined. Then, add the egg, vanilla extract, and milk, stirring until smooth.
Combine Wet and Dry: Gradually add the dry ingredients to the wet mixture, stirring gently until just combined. Be careful not to overmix, as this can make the muffins tough. If using chocolate chips or nuts, fold them in at this stage.
Fill Muffin Cups: Divide the batter evenly among the 12 muffin cups, filling each about 3/4 full.
Bake the Muffins:
Bake: Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Cool: Allow the muffins to cool in the pan for about 5 minutes, then transfer them to a wire rack to cool completely.
Serve:
Enjoy your fluffy and flavorful Peanut Butter Banana Muffins as a quick breakfast, snack, or dessert. Store any leftovers in an airtight container at room temperature for up to 3 days.