Combine flour, sugar, cocoa powder, baking powder, and salt in a bowl. Make a well in the center of the flour mixture. Pour milk, egg, and oil into the well and mix until moistened.
Heat a griddle over medium-high heat. When a few droplets of water bounce on the surface of the griddle, it is ready. Spoon batter onto the hot griddle by the tablespoon for mini pancakes. Cook until bubbles form and edges are dry, 1 to 3 minutes. Flip and cook until browned, 1 to 3 minutes more. Repeat with remaining batter.