Trust me on this one and use salted butter in this icing.
Whip that butter, with a paddle beater if you have it, if not, don't worry.Add in the icing sugar* make sure it's fresh!*Add in the cream. Not milk, cream. I used 4 tablespoons for my preference, you adjust to what you want.Stiffer icing = less cream.
Whippier icing = more cream.
Add in the vanilla,
Then keep mixing it until fluffy and thoroughly combined