Pre-heat oven to 350F (180C), lightly grease a cookie sheet.
In a medium bowl whisk together the flour and baking powder.
In a large bowl beat the butter and sugars until light and fluffy approximately 5 minutes, then add the egg, banana and vanilla beat to combine. Add the whisked flour mixture a little at a time and combine with a wooden spoon or spatula. Then stir in the chocolate chips and chopped nuts.
Drop by spoonfuls on the prepared cookie sheet. Bake for approximately 12-15 minutes. Enjoy!