Good sugar cookies deserve a good finish. This icing sets firm enough to stack and pack, yet it still bites softly instead of cracking like a rock. It’s sweet, full of vanilla, and easy to tint in whatever colors your occasion calls for. All you need is a bowl, a whisk and a few pantry staples.
Ingredients
- 4 cups powdered sugar (480 grams)
- 5 to 6 tablespoons milk, divided, plus more if needed (75 to 90 ml)
- 4 teaspoons light corn syrup
- 1 teaspoon pure or clear vanilla extract
- Optional: Gel or liquid food coloring
How to Make Sugar Cookie Icing
Step 1: Mix the Base
Put the powdered sugar in a large bowl and add 5 tablespoons of the milk, the corn syrup and the vanilla. Whisk until everything is blended and you can’t see any lumps. At this stage the mixture will be quite stiff, and that’s expected.
Step 2: Thin to Outline Consistency
Stir in more milk, just 1 teaspoon at a time, until the icing loosens up. To check it, lift your whisk or spoon out of the bowl and watch the icing drip off. It should fall in ribbons that take about 3 to 4 seconds to sink back into the surface. If it’s too runny, whisk in a bit more powdered sugar. If it’s still too thick, add a little more milk.
Step 3: Add Color and Set Aside the Outline Icing
If you’re tinting the icing, stir in your food coloring until the shade is even throughout. Then scoop out about one-third of the icing and set it aside. This portion will be used for outlining.
Step 4: Make the Flood Icing
Take the remaining two-thirds and thin it further, adding only ½ to 1 teaspoon of milk at a time. You’re aiming for a looser texture. When you lift the whisk, the icing should melt back into the bowl almost right away, with the surface smoothing itself out quickly.
Step 5: Decorate the Cookies
Spoon the thicker icing into one piping bag and the thinner icing into another. Snip a tiny opening off the end of each bag. Pipe a border around the edge of each cookie first, then fill the inside with the thinner icing. If you spot any gaps or air pockets, nudge the icing into place with a toothpick.
Step 6: Let Them Dry
Arrange the decorated cookies in one layer inside an airtight container and leave them alone. The icing needs roughly 20 to 24 hours to harden completely before you can stack them.
Tips for Success
- Add milk slowly. A little liquid goes a long way. Small additions keep you from overshooting and ending up with soupy icing.
- Do the ribbon test. Checking how long the icing takes to settle is more reliable than judging by eye.
- Sift if needed. If your powdered sugar has clumps, sifting it first saves you from fighting lumps later.
- Use gel coloring for bold shades. Gel colors are more concentrated, so you can get deep tones without watering down the icing.
- Cover leftover icing. Icing crusts over quickly, so keep unused bowls covered while you work.
Substitutions and Variations
- Milk: Whole, 2%, 1%, skim and almond milk all work. Water can stand in at the same amount, though milk gives a slightly better result.
- Corn syrup: It adds shine and helps the icing set faster. You can leave it out and add a little extra milk instead.
- Vanilla: Choose clear vanilla if you want bright white icing. Pure vanilla will give a faint ivory tint.
- Multiple colors: Once the icing reaches outline consistency, split it into several bowls, tint each one, then divide each color into outline and flood portions.
Make-Ahead and Storage
You can prepare the icing in advance and keep it in a sealed container in the refrigerator. When you’re ready to use it, let it come to room temperature and stir well. It may need a splash of milk to return to the right texture.
Decorated cookies are best made the day before serving. Keep them in a single layer in an airtight container so the icing stays intact and the designs don’t smudge.