Combine flours, baking powder, and salt. With an electric mixer, cream the butter and sugar. Add banana, peanut butter, milk, and egg, and mix until well combined. Gradually add the flour mixture and beat until just combined. Use a rubber spatula to stir in any excess flour, then stir in chocolate chips.
Evenly divide batter between two greased 8x4 inch loaf pans. Bake at 350F for 40-45 minutes, until a toothpick inserted into the loaves comes out clean. Cool completely before cutting.