Every year for the first few years of making sugar cookies as a wife and then a wife and mother, I struggled with this concept. The frosting would either be like cake frosting (and never harden but be soft and fluffy) or like a runny river that never hardened and simply made a big mess.
So, I turned to that old trusty friend, the-site-formerly-known-as-Recipezaar (Food.com). And, there, I found the recipe of my (and Muffin’s) dreams!
How does such a lovely frosting get made? Well, here I am to show you.
Sugar Cookie Frosting (That Hardens)
2 cups sifted confectioner’s sugar
1 tablespoon milk + more if needed to thin it out
1 tablespoon light corn syrup
1/2 teaspoon vanilla extract (or 1/4 teaspoon other flavoring)
In a small bowl, mix confectioner’s sugar with milk. Add more milk, as necessary, to reach a spreading consistency. Beat in syrup and flavoring until smooth and glossy. Divide into bowls and tint with food coloring.
To use frosting: paint cookies using a brush.