Combine the frosting and one cup of powdered sugar in a large bowl.

Use an electric mixer to mix well.

Turn off the mixer and slowly add the second cup of powdered sugar. The dough should be only slightly sticky.

Dust a work surface with powdered sugar.

Turn out the frosting and sugar mixture onto the work surface.

Knead mixture until it is smooth and no longer sticks to your hands and fingers. You may need to add a bit more sugar to reach this consistency.

Scoop the solar system edible playdough into individual jars with lids and keep in the refrigerator until ready for use. Let the dough sit out for 10 to 15 minutes to soften before play.