Preheat the oven to 350°F. Line an 8.5x4.5-inch loaf pan or 9x5-inch loaf pan with parchment paper, letting it hang about an inch above the sides. Butter any exposed sides.
Make the batter. Mash bananas well with a fork (I like to do this on a flat surface like a board or a plate to make easy work of it). Combine mashed banana with brown sugar in a large bowl until sugar dissolves. Whisk in maple syrup, eggs, oil and vanilla until smooth.
Combine flour, baking powder, baking soda, cinnamon, nutmeg and salt in a medium bowl and whisk to blend evenly. Add the dry ingredients to the banana mixture and fold it in gently until moistly absorbed, but a few streaks of flour remain. Add the pecans and chocolate chunks and fold them in gently until just combined. Do not over mix.
Spread batter into prepared pan. Sprinkle extra chopped pecans on top, then sprinkle the sugar evenly over the top as well. Bake for 45-55 minutes until the top is evenly browned and a skewer inserted in the center comes out clean.NOTE: an 8.5x4.5-inch loaf will take longer to bake – closer to 55 minutes.
Transfer pan to a wire rack and let cool for 15 minutes. Lift the loaf from the pan using the parchment overhang and let cool for at least an hour on the rack before slicing.