the red velvette icing I use has a base of flour sugar and milk. that is cooked to a thick paste. cooled and then butter is beaten in.
It is then spread on a cooled cake.
Hope this helps.
PS anytime a frosting is too soft you can beat in a little shortening until emulsified with the other ingredients this will give even the limpest frosting the backbone it needs...but you do lose a little of the rich original flavor.