
In a large mixing bowl, whisk together the flour, sugar, baking soda, and salt.
In a medium bowl, whisk together the buttermilk, sourdough starter, and eggs.
Add the wet ingredients to the dry ingredients and fold together a few times. (There should still be dry spots of flour.) Add the butter and gently stir until combined. (The batter should be lumpy). Set aside for 5 minutes while the waffle iron preheats.
Once ready, grease the waffle iron with more melted butter or nonstick spray. Work in batches to add about ⅓ cup of batter to each waffle section of the iron (or the amount suggested for your particular waffle iron). Cook for 3 to 4 minutes until the waffles are golden brown. Place the waffles on a wire rack to cool slightly, or hold warm in a 200°F oven.
Serve warm with butter, maple syrup, or fresh berries.