In a large bowl, combine the flour, sugar, baking soda and salt. In another bowl, combine the mayonnaise, bananas and vanilla; stir into dry ingredients just until combined.
Spoon 1 tablespoon of batter into each paper-lined muffin cup. Top each with a chocolate kiss, pointed side down. Fill cups two-thirds full with remaining batter.
Bake at 350° for 20-25 minutes or until a toothpick comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
In a bowl, combine the peanut butter, confectioners' sugar, vanilla and enough milk to achieve spreading consistency. Frost cupcakes. Garnish with chocolate chips if desired.