Mix all ingredients with an electric mixer until smooth. Add more milk or more powdered sugar to achieve your correct consistency.
If you are coloring the icing, divide it into bowls to color. Gel food coloring works great.
Use squeeze bottles to decorate cookies or a spatula. This will dry nicely in a few hours allowing cookies to be stacked.
Add on any sprinkles or crushed candies before icing sets. Enjoy!