4 c powdered sugar (also called confectioner's sugar) makes 1 pound. Boxes usually are 1-lb.
3-oz. pkg cream cheese, softened (low-fat ok, but not non-fat)
2 1/4 c powdered (confectioner's) sugar
1 t vanilla
1/4 c milk (Mama's recipe calls for "top milk or cream." I use non-fat now; she used regular full-fat milk back then and probably doesn't even make this now!)
Mix. Yield: enough for a 9x13 cake-pan cake. Kind of skimpy for a two-layer cake, though it may be extended without damage by using 2 T more milk and however much more powdered sugar is needed to result in the correct spreading consistency.
Mama taught me a trick to make a 2-layer cake more stable. Put the bottom layer upside-down on the serving plate; this means a flat surface is up. Put on the top layer right-side up, which means a curved surface is up as it should be. But the flat layers will face each other, thus adding stability and making icing easier.
She also taught me about how to anchor sliding layers with toothpicks.
2 boxes (2 lbs.) powdered (confectioner's) sugar 1/4 c water 3/4 c shortening 2 t flavoring color as desired
Mix and fill pastry bag(s).
To make bags more cooperative, fold down the top of the "sleeve" and set the bag, tip down, in a glass or cup to support the bag.
1 box (1 lb.) powdered (confectioner's) sugar
1/2 t cream of tartar
Mix and pastry bag(s).
Takes about 1 hr to set up. Allow overnight for final curing.
This icing dries out quickly, so keep bowl(s) of extra icing covered with a slightly-damp tea towel. And don't dawdle. Have what you're going to decorate set out and ready.