In a mixing bowl, combine mashed banana, flour, sugar, baking powder, and salt.
In a separate bowl, whisk together milk, egg, and melted butter. Add the wet ingredients to the dry ingredients and mix until just combined.
Heat a non-stick pan over medium heat and lightly grease with vegetable oil. Pour 1/4 cup of batter onto the pan for each pancake.
Cook for 2-3 minutes until bubbles form on the surface, then flip and cook for another 1-2 minutes until golden brown. Repeat with the remaining batter.
In a small saucepan, combine chopped pecans, brown sugar, maple syrup, cinnamon, and vanilla extract. Cook over medium heat, stirring constantly, until the pecans are caramelized, about 3-4 minutes.
To assemble the pancake tower, stack the pancakes on a plate, alternating with layers of caramelized pecans. Drizzle any remaining caramel sauce over the top.