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The Ultimate Sugar Cookie Icing That Hardens: Smooth, Glossy Royal Icing Recipe for Decorating

Close-up of star-shaped sugar cookies decorated with white and red cookie icing and sprinkles.
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You need a reliable recipe for sugar cookie icing that hardens completely, giving your decorated cookies a smooth, glossy, and durable finish perfect for stacking and gifting. This guide shows you how to make professional-quality royal icing that sets beautifully.

Ingredients

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  • 3 tablespoons Meringue Powder
  • 1/2 teaspoon Vanilla Extract (or clear extract for pure white)
  • 1/4 teaspoon Cream of Tartar
  • 4 cups Powdered Sugar, sifted
  • 6 to 8 tablespoons Water, cool

Instructions

  1. Combine the meringue powder, vanilla extract, and cream of tartar in the bowl of a stand mixer fitted with the whisk attachment.
  2. Add 6 tablespoons of cool water and mix on low speed until just combined. Let the mixture sit for 5 minutes to allow the meringue powder to fully hydrate.
  3. Add the sifted powdered sugar to the bowl. Start mixing on low speed until the sugar is incorporated, then increase the speed to medium-high.
  4. Beat the icing for 5 to 7 minutes until it is very thick, bright white, and holds stiff peaks. This develops the structure needed for hardening.
  5. Test the consistency. For piping details, the icing should be thick. For flooding, add water one teaspoon at a time until the icing flows slowly off the whisk and the trail sinks back into the bowl in about 10 seconds (this is the 10-second rule for flooding consistency).
  6. Divide the icing into bowls for coloring, if desired. Use gel food coloring for the best results without thinning the icing.
  7. Use the thick icing for outlining cookies. Let the outline dry for 15 to 30 minutes before filling (flooding) the center with the thinner consistency icing.
  8. Allow the decorated cookies to dry uncovered at room temperature for 6 to 12 hours, or until the icing is completely hard to the touch.

Notes

  • To achieve a glossy finish, avoid over-beating once the icing is smooth. Adding a drop of clear vanilla extract helps maintain shine.
  • If your icing is too thin for piping, add powdered sugar one tablespoon at a time until you reach piping consistency.
  • If your icing becomes grainy, it means the powdered sugar was not fully dissolved. Beat the icing longer, or add a few drops of water and beat again.
  • For the best results when stacking or gifting, allow the icing to dry for a full 24 hours in a dry environment.

Nutrition

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