Preheat the oven to 350F. Mash the bananas with a fork and set them aside.

Combine flour, baking powder, baking soda, salt together and set aside.

Using a standing mixer or a regular hand electric mixer, beat the butter and sugar until light and fluffy. Add eggs and vanilla extract and keep mixing. Add the mashed bananas and mix everything well.

Add the walnuts and white chocolate chips. Do not overmix the batter.

Cover a cookie sheet with parchment paper or lightly grease with oil and drop dollops of batter using a spoon or a medium ice cream scoop, spacing them about 2 inches apart.

Bake for about 14-15 minutes or until the cookies are golden brown. Transfer cookies to a wire rack and let them cool completely.