In a bowl of an electric mixer fitted with the whisk attachment, combine the powdered sugar, meringue powder, 5 tablespoons of water, and vanilla extract.

Mix for 1-2 minutes on low speed, scraping down the sides to make sure everything has been incorporated. This will help ensure you also don’t get a big cloud of powdered sugar all over your kitchen.

Turn the speed to medium-high, and mix an additional 3-4 minutes until the ingredients are well blended, the royal icing has increased in volume, and the icing has a relatively matte finish. Note, if you’re using a hand mixer instead of a stand mixer, this will take closer to 8-10 minutes. The royal icing will be thick; This is the base consistency to start with. Royal icing dries out quickly, so make sure it is covered at all times with a wet paper towel or wet kitchen towel unless it’s in a pastry bag.

I usually add about 1 teaspoon more of water for a good outline icing (I use a 15-second rule, meaning if you drizzle the icing with a spoon or spatula over the bowl of icing it will melt back into the icing in 15 seconds. Depending on how thin your icing needs to be you can add anywhere from 1-4 more tablespoons of water, as needed. Go slowly, adding ½ teaspoon at a time at most, as it's easier to thin out your icing than it is to make it thicker again.

If your royal icing is too thin, you can add small amounts of powdered sugar to thicken it, but I prefer to add just small bits of water at a time to ensure my royal icing doesn’t get too thin.

Add gel food colorings a little at a time as needed to color the icing. The color will deepen as it sits.