In the bowl of your electric mixer, whisk together the powdered sugar and meringue powder. With the speed on low, slowly add 1/2 cup of water. The mixture might look a bit lumpy and thick. Keep adding water, if necessary, and mixing until the mixture is thick but smooth, like honey.
Beat the mixture on medium speed for about 3-4 minutes, until the icing is fluffy and thick and stop as it forms stiff peaks. If you dip a whisk into the icing, the icing should stay on the whisk and not fall down immediately.
Divide icing into two small mixing bowls or jugs (somethinglike Pyrex measuring cups). Add a few drops of food coloring to each one and whisk until the icing is evenly colored. To prepare the icing for piping add a drop of water to each, then whisk it in. Keep adding water until the icing is a tad less thick, similar to toothpaste.
OUTLINE: Spoon some icing of each color into two pastry or disposable bags, fitted with a small round tip (I used size 4). Twist bags at the end, pushing icing towards the tip. Outline the cookies. If you want a cookie of 2 colors, also make the dividing lines within the borders.
FLOOD: Add a few drops of water to each of the bowls with icing and stir until incorporated. You want the icing to be easily spreadable, but still somewhat thick, similar to honey. Because of the shape of these cookies, it is best if you transfer the icing to small plastic bottles, which make flooding very easy. Flood the cookies, I made about 1/2 pink and the other yellow. Push icing towards the edge with a toothpick.
When all the cookies are flooded let them set for about 5 minutes, then sprinkle with sprinkles or make small dots with the icing leftover in the bags you used for outlining.
Let cookies dry completely before adding the jam, for a few hours or even overnight.
Assembly: Spread 1-2 tablespoons of jam over each “bottom” cookie, but don’t let it reach the edge. Add the top “doughnut” cookie and gently press it down, this will push the jam towards the outer edge. If any jam is dripping over, wipe it away. Do this with all the cookies, then arrange them on a platter and cover with plastic wrap. Store at room temperature.
Royal icing recipe adapted from Sweet Sugarbelle, which also has a ton of useful tips! Definitely worth checking out.