Cream butter and shortening in mixer. Beat in vanilla.

Gradually add powdered sugar. Scrape often.

Add water and beat on medium until light and fluffy. If too stiff, add water. If too thin, add powdered sugar.

Cover tightly with plastic wrap. Can stay at room temp a day or so, then refrigerate

* 1.5 cups Crisco - 11 ounces by weight

** 1 pound powderd sugar = 3-1/2 to 4 cups unsifted. 4-1/2 cups sifted