A light, tangy batter that works perfectly to make either breakfast favorite (because obviously the kids can't ever agree on which one to make)!
1. Whisk the ingredients for the overnight sponge together in a large bowl, cover (preferably with anything environmentally friendly and not plastic wrap), and let sit on the counter at room temperature at least 8 but no more than 12 hours*.
2. Melt butter in microwave-safe bowl.
3. Whisk together egg, kosher salt, and vanilla extract in a small bowl.
4. Preheat waffle iron (**see notes).
5. Sprinkle baking soda on top of overnight sponge.
6. Add butter and egg mixture to overnight sponge and whisk vigorously to combine and aerate.
7. Cook waffles and serve immediately (topped with syrup, nutella, peanut butter & jelly, etc.) or place on a wire rack on a cookie sheet in a warm oven (~155 F).
*Don't sweat it if you forget to make the sponge the night before! You can still mix the sponge as directed and then place into a cold oven with the light on. The heat will help jumpstart the fermentation process. It won't be as delicious and tangy as an overnight ferment, but a few hours in the oven with the light on will work enough magic.
**If you wan't good sourdough waffles, you need to invest in a good waffle maker. It needs to be able to maintain high heat even in the presence of massive amounts of evaporation from these (or any) waffles. We prefer the VillaWare model 2002 on heat setting 4.5.
***Freeze extra waffles in a sealed container between squares of parchment paper. To reheat, wrap frozen waffle in parchment paper and microwave for 30 seconds. If you prefer a crispier waffle, microwave 20 seconds and then lightly brown in toaster