This is the Wilton recipe that I was taught in cake decorating classes years ago and I've used it on my decorated cakes for years and people just rave about it. This frosting tastes wonderful and it crusts nicely. It accepts tints well and can be used for piping borders or anything else you may need for decorating. You can make it a little bit stiffer and it makes lovely icing flowers or make it a little thinner for delicate string work or writing. Use it to frost and decorate your favorite kind of cake. Enjoy!
In a large bowl, beat shortening and butter with an electric mixer until light and fluffy. Beat in vanilla.
Add sugar one cup at a time, beating after each addition on medium speed. Scrape sides and bottom of bowl often. NOTE: By the time you have all of the sugar mixed in, the icing will appear very dry. This is normal.
Gradually add in milk. Beat at medium speed until light and fluffy.