Combine the dry ingredients: In a large mixing bowl, whisk together the sifted flour, baking powder, salt, and granulated sugar until well blended. Visually, the mixture should be uniform and free of lumps.
Mix the wet ingredients: In a separate bowl, whisk together the milk, egg, and melted butter until the mixture appears smooth and slightly frothy. Look for a light, homogenous mixture with no streaks.
Combine wet and dry: Pour the wet mixture into the dry ingredients and gently fold with a spatula just until combined. The batter should be slightly lumpy but without dry flour pockets.
Prepare the cinnamon-sugar swirl: In a small bowl, mix the brown sugar and ground cinnamon until evenly combined. Set aside.
Cook the pancakes: Heat a non-stick skillet or griddle over medium heat until hot, and lightly grease if necessary. Pour a scoop of batter onto the skillet and immediately sprinkle a tablespoon of the cinnamon-sugar mixture onto the batter. Use a skewer or toothpick to gently swirl the cinnamon sugar into the batter to create a marbled effect. Cook until bubbles form on the surface and the edges look set, about 2-3 minutes, then flip and cook for another 2 minutes until golden brown.
Finish cooking: After flipping, wait until the pancake's underside is golden brown and the top is cooked through. Remove from the skillet and keep warm. Repeat with remaining batter, swirling in cinnamon-sugar as desired. Serve stacks topped with syrup or toppings of choice.
