Seeking frosting recipe

I took a cake decorating class some years ago and got a recipe there for icing. It was like a buttermilk icing but didn't use butter or milk. I can remember that it used powdered sugar, shortening, butter and vanilla extract, water and salt. I can't remember the measurements and I can't find the recipe. Does anyone know this one? My mother used to make one similar but without the salt and I really did prefer the salt. Any help is more than appreciated! Thanks, Sarah