Step 1: In a large bowl, whisk together the flour, granulated sugar, baking powder, baking soda, and salt. Make sure there are no lumps.
Step 2: In a separate medium bowl, whisk together the egg yolks, buttermilk, melted butter, and vanilla extract until well combined.
Step 3: Pour the wet ingredients into the dry ingredients. Mix with a whisk or spatula until just combined. Be careful not to overmix; a few lumps are fine. Overmixing develops the gluten, leading to tougher waffles.
Step 4: In a clean, separate bowl, beat the egg whites with an electric mixer on medium-high speed until stiff peaks form. This usually takes 2-3 minutes. The whites should hold their shape when the whisk is removed.
Step 5: Gently fold the whipped egg whites into the waffle batter in two additions. Use a spatula and a delicate, lifting motion to incorporate the whites without deflating them. This step is crucial for light and fluffy waffles.
Step 6: Preheat your waffle iron according to the manufacturer’s instructions. Lightly grease with cooking spray or butter if your waffle iron isn’t non-stick.
Step 7: Pour or scoop the batter onto the hot waffle iron, filling it about two-thirds full. Close the lid and cook for 3-5 minutes, or until the waffles are golden brown and crisp. Cooking time will vary based on your waffle iron.
Step 8: Carefully remove the cooked waffles and serve immediately with your favorite toppings. Repeat with the remaining batter. For best crispness, do not stack hot waffles; place them on a wire rack to prevent steaming.