This same recipe can be used for pancakes, if you prefer.
227 grams sourdough starter
241 grams all-purpose flour
28 grams sugar
454 grams buttermilk
all overnight sponge
2 large eggs
57 grams melted butter
3/4 teaspoon salt
1 teaspoon baking soda
To make the overnight sponge, stir down your refrigerated starter, and measure out 1 cup (227 g).
In a large mixing bowl, stir together the 1 cup starter, flour, sugar, and buttermilk.
Cover and let rest at room temperature overnight.
In a small bowl or mixing cup, beat together the eggs and butter. Add to the overnight sponge.
Add the salt and baking soda, stirring to combine. The batter will bubble.
Make waffles according to the iron manufacturer's instructions (on my iron, it takes around 3.5 minutes). (For pancakes, pour batter by the 1/4-cupful onto a heated, greased griddle; cook as you normally would
Serve immediately; or keep warm in a 200°F oven until ready to serve.