In a medium bowl, cream butter and sugar until light and fluffy.
Beat in egg, mashed banana, and vanilla extract.
Combine flour, baking powder, salt, and baking soda.
Gradually add flour mixture to creamed mixture and mix well.
Fold in chocolate chips.
Drop onto a parchment lined cookie sheet with a tablespoon 2 inches apart.
Bake at 350 degrees F for 13-16 minutes, until bottom edges are lightly browned. The tops should not be browned.
Remove to wire racks to cool.