Make batter: Heat whole milk and butter in a small saucepan over medium heat until the butter melts. Transfer to a mixing bowl and let the milk cool slightly.

Whisk egg, sourdough discard, brown sugar, apple cider vinegar and vanilla extract in to the milk mixture until no traces of egg or discard remain.

Stir in baking soda, salt and whole wheat flour until all of the flour is hydrated. Gently fold the all-purpose flour into the batter a third at a time.

Rest: Let the batter rest for 30 minutes or overnight. The rest period allows the gluten to relax, the flour to fully hydrate and starch to swell up resulting in tender and crispier waffles. Batter will be good for up to 2 days after its made.

Cook waffles: While your batter rests, preheat your waffle maker to medium high heat. Once your waffle maker is ready, cook 1 cup (226 grams) of batter for 5 to 7 minutes, or until golden brown.

Serve: These waffles are best enjoyed right out of the waffle maker. Serve with your favorite toppings.

Store: I prefer to store any leftover batter and cook my waffles fresh everytime, but these also freeze beautifully. Simply freeze any leftover waffle segments on a parchment-lined baking sheet. Store in a ziplock bag once fully frozen. For the best results, reheat in a toaster oven.