Add remaining ingredients, whisking quickly to combine thoroughly.
Pour into molds or flat container.
Freeze for a few minutes until solid.
Remove from molds or cut into squares and store in air-tight container in freezer.
Note: I make these in little square molds—though that is not necessary at all.
Notes
See instructions for making powdered sugar-free substitute here. Note that this can be made with granulated sweetener, but would have to be mixed in a food processor in that case.