Pre-heat waffle iron. In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
In another bowl, whisk together the butter and peanut butter until smooth, about 1 minute. Add buttermilk and eggs and whisk until combined, about another 1 minute.
Add buttermilk mixture to flour mixture and stir just until batter is combined.
Cook waffles according to waffle maker instructions. Serve topped with banana slices, add a drizzle with syrup, and finish it with a spoonful of marshmallow fluff.
Notes
To keep waffles warm, set a wire rack on a rimmed baking sheet. Place waffles on the wire rack and place in a 275 degree oven.