In a large bowl, combine the flour, cocoa powder, sugar, baking powder, baking soda, and salt.
In a separate bowl, whisk the eggs. Then add the milk, melted butter, and vanilla.
Add the wet ingredients into the dry ingredients bowl, and stir to combine. Let the batter sit for 5 minutes. Meanwhile, preheat the waffle iron.
Cook the waffles:
Heat the waffle maker to your preferred setting. If your waffle maker has an adjustable temperature setting, I recommend setting it to medium-high. Grease it if necessary. The outside of these is on the crisp side, and the inside is cake-like.
Scoop some of the batter into the center of the hot waffle maker and spread it out with the back of the scoop towards the edges without over-filling it. Close the lid and cook until darker brown, about 3 minutes. Usually, when the waffle iron stops steaming, they're ready. Repeat with the remaining batter.
Serve & Store:
Serve these chocolate waffles with your favorite toppings and syrups. Refrigerate leftovers for up to 3 days or freeze for up to 3 months.
Notes
Add ½ to 1 teaspoon instant coffee or instant espresso to bring out the rich chocolate flavor of this recipe.