Same-Day Method

1. Preheat your waffle iron or waffle maker. If using a cast iron or aluminum waffle maker, be sure to lightly grease it with oil to ensure the waffles do not stick.
2. In a large bowl, whisk together the flour, sugar, salt, and baking soda.
3. In a medium bowl, whisk together the buttermilk, melted butter, and sourdough starter, and eggs. Pour the buttermilk mixture into the bowl with the flour mixture. Whisk until only a few small lumps remain. The batter should pour from a spoon but not be runny or soupy. If the batter is too thick, thin it with a little water, one tablespoon at a time.
4. Cook the batter in your hot waffle iron until done to your liking. Serve hot with maple syrup and chopped fresh strawberries or blueberries.

Overnight Method

1. The night before, in a large bowl, combine the buttermilk and melted butter. Add the sourdough starter and whisk thoroughly. Sprinkle the sugar over the top, add the flour, and whisk to incorporate. If the batter is very thick, add a little more buttermilk to loosen it. Cover and let sit at room temperature overnight (if your kitchen is warmer than 72°F/22°C, place the covered bowl in the refrigerator overnight).
2. In the morning, preheat your waffle iron or waffle maker. If using a cast iron or aluminum waffle maker, be sure to lightly grease it with oil to ensure the waffles do not stick. 
3. Take the bowl of batter out of the refrigerator. The batter will have risen in the bowl and show signs of fermentation (bubbles and a sour aroma). Sprinkle the salt and baking soda on top of the batter. 
4. In a small bowl, lightly beat the eggs, and then pour them into the fermented batter. Gently stir until incorporated.
5. Cook the batter in your hot waffle iron until done to your liking. Serve hot with maple syrup and chopped fresh strawberries or blueberries.