In the bowl of a stand mixer (or with a hand held mixer), add the dry ingredients: flour, sugar, baking powder, baking soda, salt, and cocoa powder. Mix well.
Add in the wet ingredients: milk, eggs, melted butter, and vanilla extract. Mix until all ingredients are fully incorporated. The Belgian waffle batter will be thick. Add in the chocolate chips and mix again briefly.
Pour the batter onto your hot waffle iron and cook according to manufacturer’s directions – mine basically has a setting for color – so if I set it to brown then the light switches off – roughly 5-7 min.
Serve immediately with butter, syrup, powdered sugar, chocolate ganache or any other favorite toppings.