In a large bowl, whisk together flour, sugar, baking powder, and salt until evenly combined.
In a separate bowl, whisk milk, egg, melted butter, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients. Stir with a spatula just until no dry streaks remain — batter will be lumpy. Do not overmix.
Fold in chocolate chips. Let batter rest 5 minutes while the pan heats.
Heat a non-stick skillet or griddle over medium-low heat. Add a small knob of butter; when the foam subsides, the pan is ready.
Pour ¼ cup batter per pancake. Scatter a few extra chips on the surface if desired. Cook until bubbles form across the surface and edges look set, about 2½–3 minutes. Flip once and cook 1½–2 minutes more until cooked through.
Keep finished pancakes warm on a wire rack in a 90°C (200°F) oven. Serve with maple syrup, honey, or Greek yogurt.