Add starter, flour, buttermilk and brown sugar to a large bowl, whisking to combine. Cover and let rest at room temperature overnight.
The next morning, cook butter in a small saucepan over medium heat until the butter turns a deep golden brown color (about 5 minutes). Set aside to cool.
Add egg, baking soda, cinnamon, vanilla, salt and cooled brown butter to the bowl with the starter-flour mixture, whisking just until smooth.
Preheat a waffle iron according to the manufacturer’s instructions. Brush the top and bottom plates lightly with melted butter to keep the waffles from sticking. Scoop 1/2 cup of batter in each well**, and using a spatula, spread the batter out to the corners. Close the waffle iron, and cook until golden brown.
To serve, plate up waffles and top with sliced bananas, chopped toasted pecans and maple syrup.