Glossy Royal Icing for Cookies

1. Prepare the Base Mixture

Measure out 16 ounces of powdered sugar and place it into the bowl of a stand mixer. Add the egg whites, rum, vanilla extract, salt, and cream of tartar to the powdered sugar. Use a flexible spatula to stir the mixture, forming a smooth paste.

2. Heat the Mixture

Set the bowl over a simmering water bath and continue to stir until the mixture reaches 150°F (66°C).

3. Mix to Frosting Texture

Transfer the heated mixture to a stand mixer fitted with the paddle attachment. Add the remaining 2 ounces of powdered sugar to the bowl. Mix the ingredients on low speed at first, then increase to medium speed until the icing thickens and reaches a frosting-like texture, about 20 seconds.

4. Adjust Consistency

If you prefer a thinner icing, reduce the mixer speed to low and gradually add the heavy cream while mixing until the icing is smooth. To check the consistency, use the figure 8 method: the icing should flow smoothly so that a figure 8 drawn with the icing disappears within 8 seconds.

5. Color the Icing

For colored icing, divide the icing into small bowls and cover them with plastic wrap to prevent drying out. Stir in the gel paste food coloring until you achieve your desired color.

6. Apply the Icing

Transfer the colored icing to a pastry bag fitted with a #3 tip, or use a parchment cone. Outline each cookie with the royal icing. Work quickly to prevent the icing from crusting. Then, drizzle the interior of the outline with more icing and gently nudge it into an even layer. Add sprinkles or a secondary color while the icing is still wet if desired.