Preheat oven to 400 degrees F and grease muffin tins with butter.
In a large bowl, sift together flour, baking power, baking soda, pumpkin pie spice, sugar, and salt.
In a medium sized pan over medium heat, melt the butter. Swirl occasionally to ensure butter is cooking evenly. As the butter melts, it will begin to foam and the color will get darker. Scrape bottom of pan with wooden spoon to release any brown specs. Once you start smelling the nutty aroma, remove browned butter from heat and allow to cool.
In a separate bowl, whisk eggs, buttermilk, vanilla, mashed banana, and mostly cooled browned butter together. Make a well in the dry ingredients and pour in the liquid ingredients. Fold together and do not over mix. Fold in the chocolate chips.
Spoon batter into bread pan and bake in preheated oven until golden brown, about 35-40 minutes, rotating pan halfway though cooking and moving to a lower position if top is browning too quickly. When done cooking, immediately remove from bread pan and allow to cool on cooling rack.