In a medium bowl, beat together powdered sugar, butter, and heavy cream on medium speed. Add and beat until smooth liquid of choice, vanilla and salt. Correct the consistency if necessary with powdered sugar or liquid of choice.
To store, cover the surface of the icing with a sheet of plastic wrap. This keeps for up to 3 days at room temperature or up to 3 weeks refrigerated. Or freeze for up to 6 months. Soften or beat until smooth before using.
Quick Lemon Icing
Prepare Quick White Icing, above, grating the zest of 1 lemon directly into the bowl of ingredients and using 1 to 2 tablespoons fresh lemon juice for the liquid.