Just make sure you use your unfed starter for this recipe. The first time I made it, I used fed starter and they tasted very eggy and didn't have the right texture. Don't be like me.
Unfortunately you can't whip these out in the morning. You have to make a sponge the night before and let it sit out at room temperature overnight. In the morning, you can finish the batter and make the waffles. It's only about 20 minutes of prep work, and it's really easy. I made the sponge on a Thursday night and the waffles Saturday morning, and they were worth the wait! These definitely have a different texture and flavor than regular waffles, and they're a great breakfast treat.
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2 cups flour
2 tablespoons sugar
2 cups buttermilk
1 cup unfed sourdough starter
All of the overnight sponge
1/4 cup vegetable oil or melted butter
3/4 teaspoon salt
1 teaspoon baking soda
To make the overnight sponge, stir your unfed sourdough starter and pour one cup of it into a large bowl. Add the flour, sugar, and buttermilk. Stir together, cover, and let sit at room temperature overnight. (Now you can feed your starter and use it for bread.)
The next morning, beat together the eggs and oil or melted and cooled butter. Add to the sponge along with the salt and baking soda. Stir to combine. The batter will bubble. Pour the batter into your greased waffle iron and cook according to the instructions of your waffle iron. You also could make pancakes with this batter. Serve immediately.
This made 20 individual squares in my waffle iron.
Source: King Arthur Flour