What is wet-on-wet with royal icing? It is what happens when you flood your cookie with your royal icing, immediately lay down royal icing details on top of your flood, and all the colors merge together into a beautiful smooth surface.
So, what's the best way to achieve this? First things first... mix your basic recipe first according to the recipe HERE.
Now let's take out a few tablespoons in each of the two bowls, and follow steps like this....