Preheat oven to 180 C. (350 F). Grease a 9x5 inch loaf pan, and line with parchment paper for easier removal.
Mash bananas well, either by hand or by using the paddle attachment of a stand mixer. Add egg, sugar, vanilla, and oil and mix well until combined.
Add the dry ingredients and mix until just combined and no flour streaks remain.
Fold in the chocolate chips with a spatula, don't overmix. Pour batter into prepared pan and bake for 45 minutes or until toothpick inserted in center comes out clean. Cool slightly before slicing.