Royal Icing with Meringue Powder

• Prep30 min
• Cook0 min
• Total30 min
• Serves24

Ingredients

Royal icing

• 450 g sugar (2 1/4 cups), or 450 g store-bought powdered sugar (3 3/4 cups)
• 1 tsp cornstarch, only if you mill your own sugar
• 22 g meringue powder (3 tbsp)
• 75 g warm water (5 tbsp), plus more for thinning
• Gel food coloring in the colors you like

To decorate

• Piping bags with small round tips (sizes 1 to 3), or squeeze bottles
• Toothpicks
• Cooled sugar cookies

Instructions

1. Make sure the mixing bowl, lid, butterfly whisk and spatula are clean, dry and free of any grease: even a trace of butter keeps royal icing from whipping up and drying hard. Place the sugar and cornstarch in the mixing bowl and mill 20 sec/speed 10. Wait 1 minute for the sugar dust to settle before you open the lid. With store-bought powdered sugar, skip the milling.
2. Add the meringue powder and mix 5 sec/speed 4, so it is spread through the sugar and does not form lumps when the water goes in.
3. Insert the butterfly whisk. Add the warm water and whip 6 min/speed 4, stopping after 2 minutes to scrape down the sides. Warm water dissolves the sugar and meringue powder faster, for a smoother icing. It is ready when it is bright white, glossy and stiff: a peak lifted with the spatula stands straight up. This is the stiff consistency, for flowers, leaves and borders.
4. Transfer the icing to a bowl and press plastic wrap right onto the surface. Royal icing starts to crust in the open air within minutes, and dry bits clog the piping tips. Keep every bowl covered the same way while you work.
5. For outline icing, spoon some into a small bowl and stir in water a few drops at a time with a spatula, by hand, until it looks like toothpaste and a peak bends over at the tip. Stir gently instead of beating: beating adds air bubbles that dry as tiny holes, and a few drops of water change the texture a lot.
6. For flood icing, thin another portion the same way, a few drops at a time, until a line drawn across the surface with a knife disappears in 10 to 15 seconds as you count. Faster means it is too thin and will run off the edges and dry with dents: add a spoonful of stiff icing. Slower means it is too thick to level: add a few more drops.
7. Color each bowl with gel food coloring, adding it with a toothpick and stirring by hand. Gel color is concentrated, so it does not thin the icing the way liquid drops do. Colors deepen as they dry, so for pastels stop a shade lighter than you want.
8. Fill the piping bags or bottles. Pipe an outline around the edge of each cookie, then fill the inside with flood icing, nudge it into the corners and pop any bubbles with a toothpick. Pipe raised details once the flood has crusted, about 1 hour later. Let the cookies dry uncovered at room temperature at least 8 hours, or overnight, before stacking or bagging them.

Tips

• Store leftover icing in an airtight container with plastic wrap pressed onto the surface, at room temperature, up to 1 week. It separates as it sits: stir it by hand, or whip 1 min/speed 4 with the butterfly whisk, before using.
• In Florida humidity, royal icing dries more slowly and can stay tacky. Dry the cookies in an air-conditioned room, with a fan on low if you can, and never in the fridge, where the moisture makes the icing sticky.
• Deep colors like red, black or navy need a lot of gel color and taste bitter if you overdo it. Mix them a few hours ahead or the day before: they darken as they rest, so you need less color.
• Stiff royal icing straight from the TM7 is also the edible glue for gingerbread houses and for sticking sugar decorations onto cakes and cookies.