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A flat-lay view of beautiful heart, star, and round sugar cookies decorated with smooth, glossy pastel pink, blue, and white icing. Surrounding the cookies are piping bags, cookie cutters, and bowls of colorful sprinkles on a white marble surface.

The Best Sugar Cookie Frosting That Hardens (Only 3 Ingredients!)

This easy 3-ingredient sugar cookie frosting is made without raw eggs and dries perfectly hard for stacking. It takes only 5 minutes to make and leaves a beautiful, glossy bakery-style finish!
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Prep Time 15 minutes
Cook Time 5 minutes
Resting Time 30 minutes
Total Time 50 minutes
Servings: 24 Yields
Course: Dessert, Frosting
Cuisine: American
Calories: 40
Ingredients Equipment Method Notes

Ingredients
  

  • 2 cups Powdered Sugar 240g - Also known as confectioner's sugar. Must be sifted!
  • 1 tablespoon Milk 15ml - Or heavy cream. Start with 1 tbsp, add up to 1/2 tbsp more only if needed.
  • 1 teaspoon Vanilla Extract 5ml - Or almond extract. Use clear extract if you want pure white icing.
  • 1 teaspoon Light Corn Syrup 5ml - Optional. Adds an extra glossy, reflective finish.

Equipment

  • 1 Fine-Mesh Sieve Crucial for sifting the powdered sugar to avoid lumps.
  • 1 Medium Mixing Bowl
  • 1 Whisk
  • 1 Piping Bag Optional. You can also use a Ziploc bag with the corner snipped off.

Method
 

  1. Sift the Sugar: Place your fine-mesh sieve over a medium mixing bowl. Sift the 2 cups of powdered sugar completely to remove all lumps.
    A close-up of hands holding a fine-mesh metal sieve, sifting white powdered sugar into a clear glass mixing bowl on a white marble countertop.
  2. Mix the Base: Add 1 teaspoon of vanilla extract and exactly 1 tablespoon of milk to the sifted sugar. Whisk gently to combine.
    A top-down view of a clear glass bowl on a marble counter containing sifted powdered sugar, a splash of dark vanilla extract, white milk, and a metal wire whisk resting in the center.
  3. The "10-Second Rule" Consistency Test: Check the thickness. Drag a butter knife through the center of the frosting. If the line disappears and smooths out in exactly 10 seconds, it is perfect! If it is too thick, add milk just 1/2 teaspoon at a time.
    A close-up of a white bowl filled with glossy white icing, featuring a clear line dragged directly through the center, with a silver butter knife resting beside it on a marble surface.
  4. Add Color (Optional): Divide the frosting into smaller bowls. Dip a toothpick into gel food coloring and swirl it into the frosting. Mix well.
    A top-down view of a hand using a wooden toothpick to swirl bright pink gel food coloring into a small white bowl of frosting. Other bowls of white icing and tubes of pink, blue, and yellow gel food coloring are scattered on the marble counter.
  5. Decorate & Dry: Pipe or spread the frosting onto cooled cookies. Let the decorated cookies sit undisturbed at room temperature for 12 to 24 hours to completely harden before stacking.
    A close-up of a clear piping bag dispensing smooth pink icing to outline a star-shaped cookie on a marble countertop, with a wire cooling rack filled with pastel-frosted star cookies in the background.

Notes

  • Storage: Store fully dried, stacked cookies in an airtight container at room temperature for up to 2 weeks. You can also freeze them for up to 3 months with parchment paper placed between the layers. Let them thaw at room temperature before serving.
  • Runny Frosting Fix: If you accidentally added too much liquid and your frosting is too thin, simply whisk in more sifted powdered sugar, one tablespoon at a time, until it thickens up.
  • Coloring Tip: Always use gel food coloring, not liquid drops. Liquid colors add extra moisture and can ruin the consistency, preventing the frosting from hardening.