In a large bowl, stir together buttermilk, vanilla, bananas, and melted butter.
Add flour, baking powder, baking soda, brown sugar, cinnamon, and nutmeg to buttermilk mixture, and stir until just combined.
Spray waffle iron with nonstick cooking spray and add batter according to waffle iron’s directions (I have a 4-square waffle iron, and I used 1 cup of batter per waffle).
Sprinkle waffle with pearl sugar or broken sugar cubes.
Cook waffles according to your waffle iron’s directions.
Be careful removing waffle from iron – the sugar will caramelize and will be extremely hot.
Buttermilk: Regular or low-fat buttermilk is ok. If you don't have buttermilk, you can make a substitute with this easy recipe.
Bananas: You'll want to use overripe bananas like you would when making banana bread. I like to use bananas that are yellow with a fair amount of brown speckling on them.
Pearl Sugar: Pearl sugar can be difficult to find. It's available online (Amazon) and in specialty stores. If you can't find pearl sugar, you can break sugar cubes into small chunks in place of the pearl sugar.
Freezing: I like to place the waffles on a cooling rack to let them cool to room temperature before freezing.