Preheat the oven to 350°F. Line a 9-inch loaf pan with parchment paper then grease it with cooking spray.
In a medium bowl, whisk together the mashed bananas, buttermilk, eggs, vegetable oil and vanilla extract.
In a separate large bowl, whisk together the flour, brown sugar, sugar, baking soda and salt. Add the wet ingredients to the dry and mix just until combined. Fold in the chocolate chips (optional).
Pour the batter into the prepared loaf pan.
Bake the bread until a toothpick inserted comes out clean, 50 to 60 minutes. (See Kelly’s Note.) Remove the bread from the oven and let it cool completely before slicing and serving.