Start by preheating your waffle iron according to the manufacturer’s instructions.
In a large mixing bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg.
In another bowl, combine the mashed bananas, eggs, buttermilk, melted butter, brown sugar, and vanilla extract. Mix until well incorporated.
Pour the wet ingredients into the dry ingredients and stir until just combined. Be careful not to overmix; a few lumps are okay. If using, fold in the walnuts or chocolate chips.
Lightly grease the waffle iron with melted butter. Pour the batter onto the hot waffle iron, using a ladle or measuring cup. Cook according to your waffle iron’s instructions until the waffles are golden brown and crisp
Serve the waffles warm with your favourite toppings such as maple syrup, fresh fruit, whipped cream, or a dusting of powdered sugar.