Preheat oven to 350 degrees F with oven rack placed in the middle of the oven. Grease a 12-cup standard muffin pan with non-stick cooking spray. Set aside.
Whisk together flour, brown sugar, cinnamon, baking powder, baking soda and salt in a medium bowl. Add butter and mix with your fingertips, until evenly distributed and it looks like wet sand. Set aside.
In another medium bowl, whisk together egg, mashed banana and buttermilk until smooth. Add into the flour mixture along with half of the chopped pecans and stir with a spatula until just mixed (do not over mix).
Evenly divide batter into the muffin pan (all 12 cups) and sprinkle remaining pecans on top.
Place pan in oven and bake for 17-18 minutes, until a tooth pick inserted in the middle comes clean. Do not over bake.
Place pan on a wire rack.
Serve pancake cups hot/warm with maple syrup and/or butter.