In a medium bowl, whisk together the flour, sugar, baking powder, and salt until well combined.
In a separate bowl, beat the eggs with the milk, then whisk in the sourdough starter until smooth.
Gradually mix in the dry ingredients and melted butter, stirring until you achieve a batter with the consistency of pancake batter. You can adjust with additional flour or milk if necessary. Gradually mix in the dry ingredients and melted butter, stirring until you achieve a batter with the consistency of pancake batter. You can adjust with additional flour or milk if necessary.
Preheat your waffle iron and lightly grease it if needed.