Beat first 3 ingredients in a large bowl at high speed of a mixer until smooth. Combine sugar, cocoa, and salt; gradually add sugar mixture to cheese mixture, beating at low speed until well-blended. Add vanilla, and beat well. Cover and chill.
I made this originally back in the late 90s and over the years got away from using margarine. So now I just use butter instead. This is a basic and a must for CL's Easy Fudge Layer Cake (Nov 1997). Definitely a keeper.
