Preheat oven to 350 degrees F. Grease a 5x9 inch loaf pan.
In a large bowl, mix the melted butter and maple syrup. Beat in the egg and bananas, leaving a few small chunks. Stir in the maple extract and milk.
In a separate bowl, mix the flour, baking soda, and baking powder. Stir into the banana mixture until just moistened. Transfer to the prepared loaf pan. Mix the nuts and sugar. Sprinkle evenly over the batter.
Bake 50 minutes in the pre-heated oven. Cool on rack for 10 minutes. Remove from pan and finish cooling. When completely cool, slice and serve.