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Foolproof Royal Icing That Dries Hard and Glossy for Sugar Cookies

Close-up of several round sugar cookies decorated with vibrant, hardened sugar cookie icing in rainbow colors.
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Stop struggling with sticky or runny frosting. This easy royal icing recipe hardens completely, giving your decorated sugar cookies a smooth, durable, and glossy finish perfect for stacking and gifting.

Ingredients

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  • 2 cups powdered sugar, sifted
  • 3 tablespoons milk (or water)
  • 1 tablespoon light corn syrup
  • 1 teaspoon vanilla extract
  • Gel food coloring (optional)

Instructions

  1. In a medium bowl, combine the sifted powdered sugar, milk, light corn syrup, and vanilla extract.
  2. Mix with a whisk or electric mixer on low speed until the ingredients are just combined. Do not overmix at this stage.
  3. If the icing is too thick for outlining, add milk, 1/2 teaspoon at a time, until you reach a thick, pipeable consistency (this is the ‘outline’ consistency).
  4. If the icing is too thin for outlining, add more sifted powdered sugar, 1 tablespoon at a time, until it holds a stiff peak.
  5. For flooding consistency, take a portion of the outline icing and add water, 1/4 teaspoon at a time, stirring gently until the icing flows smoothly off the spoon and the trail disappears back into the bowl within 10 seconds.
  6. Color the icing using gel food coloring, if desired.
  7. Outline your sugar cookies using the thicker icing consistency. Let the outline set for 15 to 30 minutes until dry to the touch.
  8. Flood the outlined areas with the thinner icing consistency. Gently spread the icing to the edges with a scribe tool or toothpick if needed.
  9. Allow the cookies to dry completely at room temperature. Drying time varies based on humidity, but expect 6 to 12 hours for a hard, stackable shell.

Notes

  • For the glossiest finish, use light corn syrup. It helps prevent cracking as the icing dries.
  • If you need a bright white icing, use clear vanilla extract instead of standard vanilla extract.
  • To test if the icing is truly hard, gently press the surface after drying. It should feel solid and not tacky.
  • If you are decorating for a humid event, you can lightly dust the finished cookies with a small amount of cornstarch after they are fully dry to combat any residual tackiness.

Nutrition

Find it online: https://devourdish.com/sugar-cookie-icing-that-hardens/