In a large mixing bowl, whisk together the flour, cocoa powder, sugar, baking powder, and salt until evenly combined with no lumps.
In a separate medium bowl, whisk together the milk, egg, melted butter, and vanilla extract until smooth and well blended.
Pour the wet ingredients into the dry ingredients and gently fold together using a rubber spatula until just combined. The batter should be slightly lumpy — do not overmix. Fold in 1/2 cup of the chocolate chips, reserving the rest for topping.
Preheat a griddle or large non-stick skillet over medium heat for 3-4 minutes. Lightly grease with butter or oil.
Pour 1/4 cup of batter onto the hot griddle for each pancake, spacing them about 2 inches apart. Immediately sprinkle a few of the reserved chocolate chips onto the top of each pancake.
Cook for 2-3 minutes until bubbles form across the entire surface and the edges look set and slightly dry. The bottom should be golden brown.
Flip carefully with a wide spatula and cook for another 1-2 minutes until the second side is golden and the center is cooked through.
Transfer cooked pancakes to a plate and keep warm in a 200°F oven while you cook the remaining batter. Serve immediately with butter, maple syrup, and any additional toppings you love.