This is my very favorite buttercream recipe. It is Paula Deen's, so it's extra buttery and really amazing. It is a bit thicker than the traditional buttercreams used in cake decorating, but if you whip it a bit longer it is totally workable. I do a non-dairy version of it using Nucoa non-dairy margarine (comes in the gold box) that is possibly even better than the regular. I love to use that one when I'm making cakes for kiddos who have dairy allergies.
This recipe makes about 5 cups of frosting
1 1/2 cups butter, softened
1 cup vegetable shortening (I use regular Crisco)
8 cups confectioner's sugar
2 teaspoons vanilla extract
In a large bowl, beat butter and shortening at medium speed with an electric mixer until creamy. Gradually beat in confectioner's sugar until smooth. Beat in vanilla.