Maple Frosting

1 stick unsalted butter (4 ounces or 1/2 cup)
1/2 cup brown sugar (light or dark, packed)

1/3 cup maple syrup (darkest grade possible)

2 1/2 to 3 cups confectioner's sugar

2 tablespoons cream, half-and-half, milk, or evaporated milk, plus more as needed

1/2 teaspoon vanilla extract

1/2 teaspoon maple flavoring, optional

In a medium saucepan over medium heat, melt the butter with the brown sugar and maple syrup.  Bring to a boil while stirring constantly.

Reduce the heat to medium-low and cook, stirring, for about 3 to 5 minutes, or until the brown sugar has dissolved.

Remove the syrup mixture from the heat and let stand until completely cooled.  

Pour the cooled syrup mixture into a mixing bowl.  Gradually beat in 2 1/2 cups of the confectioner's sugar and the cream or milk.  Add the vanilla, and maple flavoring if using, and beat until smooth and fluffy.  Add more confectioner's sugar or more cream or milk as needed to make a spreadable frosting.

Makes enough to frost an 8-inch two-layer cake, a 9x13-inch cake, or 12 cupcakes.

From TheSpruceEats.com