Preheat oven to 350 degrees F.
Grease a 24-cup mini muffin tin with cooking spray.
In a large bowl, whisk together flour, baking powder and salt.
Add brown sugar, 1/2 cup sugar and 1 teaspoon of cinnamon. Whisk to combine.
Add egg, milk and 8 tablespoons butter and stir until the mixture is smoother.
Scoop rounded tablespoons of batter into the greased muffin tin.
Bake until a toothpick inserted into the center of the muffin comes about clean, about 12 minutes.
Let muffins cool slightly in pan for about 5 minutes then carefully remove them from the pan.
Mix the remaining 1/2 cup sugar and 2 tablespoons of cinnamon in a shallow bowl.
Dunk each muffin in the remaining melted butter then toss in cinnamon-sugar mixture.
