PREP: Get all the wet ingredients to room temp before starting (see Note 2). Whisk together milk and vinegar; set aside for 5 minutes to slightly curdle (DIY buttermilk!)
DRY: Whisk together "dry ingredients" in a large bowl.
WET: Right on top, add all "wet ingredients" except the butter. Whisk until combined. While whisking, slowly drizzle in the melted butter. Whisk until smooth. Don't over-mix. Gently stir in chocolate chips. Let the batter sit for 10 minutes if possible (fluffier waffles).
COOK: Preheat your nonstick waffle maker according to the model's instructions. Once heated, add 1/3 cup of batter per cavity. Cook until each waffle is nicely crisped on both sides and cooked through in the center.
ENJOY: Keep cooked waffles warm in the oven while finishing the batch (Note 3), or serve immediately with your choice of toppings.
MAKE AHEAD WAFFLES: Waffles turn out best when batter rests for a while. I like to make the batter the night before and then cook it the next morning! To do this: cover the batter tightly and store it in the fridge overnight. In the morning, give it a quick stir and cook it in a preheated waffle maker. It's great having the batter ready to go for breakfast, and the waffles taste even better!
Notes
Note 1: My Fave Syrup: Combine 1/2 cup unsalted butter, 1 cup light brown sugar, 1/2 cup heavy cream, and a pinch of salt in a medium-sized pot. Cook over medium heat, stirring occasionally, until butter melts and syrup slightly thickens (5-8 mins). Remove from heat, stir in 1 tablespoon vanilla extract.Note 2: Make sure all wet ingredients are the same temperature or batter will get clumpy (warm butter will harden when hitting cold ingredients). Here's how I do that: Melt the butter and set aside to cool to room temp. Warm the milk slightly in the microwave or let it reach room temp naturally. Run un-cracked eggs under warm water to bring them to room temp. Note 3: To keep waffles crisp, place them on a cooling rack set over a large pan. Put the pan in a 200°F oven to keep waffles warm as you continue cooking.