Bakery Frosting

I'm not sure I agree with the Bakery Frosting name, but I didn't name it and I'm just going to keep it. I grew up eating this kind of frosting on a red velvet cake and have not used it on any other kind... yet. I do plan on using it for cupcakes next week.

Bakery Frosting

2 T cornstarch
1 c sugar
1 1/2 c milk
1/2 c shortening
1/2 c butter
dash of salt
1 t vanilla

Mix together the cornstarch and 1 t sugar in a saucepan. Add milk and stir smooth. Turn on the heat and cook over medium until thick, less than 5 minutes. Set aside to cool. Beat the shortening, butter and sugar in a bowl for about 10 minutes until very fluffy and light. Add the cooled cornstarch mixture, salt and vanilla. Beat 2-3 minutes more. Use to frost a 2 layer cake.