Mix the dry ingredients. Whisk the flour, sugar, baking powder and salt together in a medium bowl.
Mix the wet ingredients. In a separate bowl or large measuring cup, whisk the milk and egg together, then whisk in the melted butter. Pro tip: Have your milk out at room temperature and let your melted butter cool to prevent butter from hardening. Combine wet & dry ingredients. Combine milk mixture with dry ingredients just to moisten. The key to keeping your pancakes light & fluffy is to not overmix them. A few small lumps are fine.
Rest the batter and heat the skillet. Leave the batter undisturbed for a few minutes while you warm a large skillet over medium heat. Add a small pat of butter and swirl to coat the surface.
Cook until golden. Spoon about 3 tablespoons of batter into the skillet for each small pancake, or more for a larger one. Leave room to flip. Cook for 1–2 minutes, until the edges look set and a few bubbles have opened on the surface. Flip with a thin spatula and cook for another 1–2 minutes, until golden underneath and cooked through. Larger pancakes may take a little longer.
Finish the batch. Transfer the pancakes to a warm plate or the prepared baking sheet. Repeat with the remaining batter, greasing the skillet lightly between batches as needed.