Prepare the Oven: Preheat the oven to 375°F and line a cupcake pan with cupcake liners.
Cream the Butter: Beat the butter and brown sugar together until the mixture becomes light and fluffy.
Add the Egg: Add the egg to the butter-sugar mixture and beat until incorporated.
Blend in the Maple Syrup: Pour in the maple syrup and mix until it is thoroughly combined with the batter.
Combine the Dry Ingredients: Add the flour, baking powder, and salt, mixing until the ingredients are just beginning to come together.
Add the Milk: Pour in the milk and continue mixing until the batter is fully combined.
Fill the Liners: Spoon the prepared batter into the lined cupcake pan.
Bake the Cupcakes: Bake at 375°F for 18–22 minutes, until the cupcakes are baked through.
Cool Completely: Remove the cupcakes from the oven and allow them to cool completely before frosting.
Prepare the Buttercream: Beat the butter until it is soft and smooth, then add the powdered sugar and maple syrup and beat until the frosting reaches the desired texture.
Frost the Cupcakes: Pipe or spread the maple buttercream over the completely cooled cupcakes, then serve and enjoy.