As promised, here is the royal icing recipe (+ mini decorating tutorial) you can use to decorate rolled cookies. There are two alternatives for this recipe: you can use liquid pasteurized egg whites or meringue powder. I’ve had success with both.
Royal Icing Ingredients
2 cups icing sugar (260 g)
3 tbsp. liquid pasteurized egg whites (OR 2 tsp. meringue powder + 3 tbsp. warm water)
1 tsp. vanilla
Water to thin icing to desired consistency
Add all ingredients to a mixing bowl and mix on high with an electric mixer for 10 minutes. I will explain, a little later in the post, why these 10 minutes are important. Once you have mixed for 10 minutes, the icing should be thick and fluffy. Add water SLOWLY (a few drops at a time) until you reach your desired consistency. Remember that it is easier to add more water to thin out the icing than it is to add icing sugar to thicken it. You may also add food colouring but remember that liquid food colours will thin the icing (so keep that in mind when you are thinning the icing with water.) Also, the amount of water you add could vary each time you make the icing. Humidity and temperature can affect how much water will be needed.
The icing consistency will be different, depending on what you are using it for. To pipe details onto a cookie, a thicker icing should be used. To flood the surface of a cookie, a thinner icing is easier to work with because it doesn’t dry as quickly. The basic technique with royal icing is to use a thick icing to pipe a border around the cookie and then fill in the border with a thinner icing. You can also get away with using the same icing for piping and flooding if you have a medium consistency. It is all personal preference; just experiment with it and see what works for you. It is hard to say exactly how thick the icing should be because decorating cookies is more an art than a science (well… duh.) The 10 second rule seems to be a good way of checking if your icing is a good consistency. Drag a knife through the icing and count how long it takes for the surface of the icing to smooth out again. If it takes less than 10 seconds, your icing is probably just right. If it takes less than 5, however, your icing might be too thin.
For piping details, you don’t want your icing to just ooze out of the tip. It should be thick enough that you can make loops with the icing and have them remain distinct from each other. On the other hand, if you find yourself having trouble squeezing the piping bag, or the icing is not sticking well onto the cookie, your icing is too thick. For flooding a cookie, you want the icing to be thin enough that if you pipe loops, they will flow together.
I highly recommend using gel or concentrated food colouring. I never seem to be able to get the colour I want if I use liquid food colouring. With concentrated food colouring, you can actually get deep, rich colours (even black) instead of just pastel ones. Dip a toothpick into the colour and spread it around in the icing. Then blend the icing with a spoon or fork. As you can see, I use empty yogurt containers to store the icing when I’m not using it. Royal icing dries out very quickly so once you have your desired colour, make sure the icing is covered. If storing icing in its container for a while, it is a good idea to put a bit of plastic wrap on top of the icing to prevent a skin from forming. Otherwise, put the icing directly into a piping bag with a tip. Twist the piping bag and secure with a rubber band to prevent the icing from drying out. If putting thin icing in a piping bag, be careful to position the tip upwards when not in use so that the icing doesn’t ooze out everywhere. To prevent this oozing problem, thin icing for flooding can also be put into a plastic squeeze bottle instead of a piping bag.
Begin by piping a border around the cookie. Allow the outline to dry and then flood the cookie. Use a toothpick the help bring the icing out to the edges.
To add details in another colour while the icing is still wet, pipe a design directly onto the wet icing. A toothpick may be dragged through the icing to create a marble effect. Two types of effects are shown in the photos below.
You can also wait for the icing to dry and then pipe on extra details, which will give an extra dimension to the cookie.
When you are finished decorating the cookies, they must dry for 24 hours. Otherwise, the icing may get smudged or colours may bleed. Once the icing has been allowed to dry sufficiently, cookies should be stored away from moisture. Humidity can ruin designs on cookies by causing the colours to run. Bleeding of colours can also result if the two icings used in the design have different consistencies. This is due to diffusion. If there are more water molecules in one icing than another, the water molecules will move through the icing to even things out. This water movement between the two icing colours causes the design on the cookie to look fuzzy.
Glaze vs. Royal Icing
This picture demonstrates the importance of beating the icing for 10 minutes.
On the left, is icing sugar, water, meringue powder, and food colouring all mixed together briefly with a fork. On the right, is the exact same icing, after it has been beaten for 10 minutes. The icing on the left is more a glaze than royal icing because it is thin and transparent. The egg in this icing hasn’t been whipped up to be thick and fluffy. On the right, is true royal icing. It is thick and much easier to work with, but still fluid enough to flood the cookie. Unlike the glaze, it doesn’t spread out quickly and run off the cookie. Also, notice that the colour got much lighter after it was mixed for 10 minutes. Think of the process of making meringue. When you start, the egg whites are a clear, yellowy-white colour. You begin to beat the egg whites and they become frothy, and eventually thick, glossy, and opaque. This thickening of the egg white is also what is happening in the royal icing. The protein molecules in the egg white are like little clumps of folded up wire. When you beat the egg whites, the proteins begin to unfold (this is called denaturation.) As you incorporate air into the egg whites, the unfolded proteins start surrounding the air bubbles and begin to aggregate. This creates a sort of “protein shell” around the air bubbles, which gives stability to the thickened egg whites. Adding acid during this thickening process helps because it aids in the denaturation process. This is why many meringue or royal icing recipes will call for lemon juice or cream of tartar (both are acidic.) I don’t like my royal icing to taste lemony or sour so I opted against adding an acid. The meringue powder already has acid present in it and it is still possible to whip up egg whites without acid; they may just not get as thick. Another option is to add a pinch of salt to the mix. Like acid, salt also helps denature proteins. And there you have it: why it is necessary to beat the icing for 10 minutes.
I’m currently in the process of decorating some Christmas cookies with my sister. It takes a while waiting for the icing to dry, and so far we’ve done mostly practice cookies that don’t look the best. I find that it usually takes a bit of practice to get back into decorating cookies with ease. I will post pictures once we are finished