01 - Preheat oven to 350°F and line a 12-cup muffin tin with cupcake liners.
02 - Whisk together flour, baking powder, and salt in a large bowl; set aside.
03 - Beat butter and sugar until light and fluffy. Add mashed bananas and mix until combined.
04 - Beat in eggs one at a time, then stir in vanilla extract.
05 - Gradually add dry ingredients to banana mixture, alternating with milk; mix just until combined.
06 - Divide batter evenly among cupcake liners, filling each about 2/3 full.
07 - Bake for 16-18 minutes, or until a toothpick inserted into the center comes out clean. Cool completely on a wire rack.
08 - Beat butter until fluffy, then gradually add powdered sugar. Mix in banana milk and vanilla. Blend in extra mashed banana if desired.
09 - Pipe or spread frosting onto cooled cupcakes. Garnish with whipped cream, maraschino cherry, and straw for milkshake presentation.