1Preheat the oven to 350 degrees. Spray a 9 inch by 5 inch loaf pan with cooking oil spray. Set aside.
2Combine the butter and sugar in the bowl of a stand mixer fitted with the paddle attachment. Mix on medium speed until the mixture looks light and fluffy. Add one egg at a time, beating well each time. Add the vanilla and bananas to the mixture and mix well on medium speed.
3In a small bowl, sift together the flour, baking powder and salt. With the mixer running on its lowest speed, add the flour mixture to the bowl little by little, until just combined.
4Add the walnuts and chocolate chips to the batter and mix until just combined. Pour the batter into the prepared loaf pan and spread with a spatula to even it out.
5Slide the pan into the preheated oven and cook for about 1 hour. The bread is done when a toothpick inserted in the center comes out clean. Let cool before slicing and serving.