Melt the butter in a small pot and let it cool down a little. Mix flour, sugar, baking powder and salt in a bowl. Whisk buttermilk and eggs. Pour into the flour mixture while stirring and mix to a smooth wafer dough. Finally stir in liquid fat.
Preheat the heart-shaped waffle iron and lightly grease it. Bake 6 waffles one after the other. Let the waffles cool down on a cake rack. Peel and slice the bananas.
Wash blueberries and drain well. Press one foam kiss each on a wafer a little bit flat. Spread banana slices and blueberries on the waffles and serve. Dust with icing sugar if necessary.