I made a batch of Edna's crusting buttercream today for a cake to be covered in MMF. I added a little way too much vanilla. I think it was supposed to be 1 tsp and I used 1 Tbsp by mistake. SO to fix it I added an 8oz block of cream cheese and 1 more pound of powdered sugar. It taste fantastic!!! I've been eating some that I left on the back of a spoon to check on crusting quality. It seems to have a great smooth consistency , no air bubbles, awesome taste and crust just fine.
Now my only problem is I'm not sure if I can use it under MMF which is what the cake is supposed to be covered with.
The cake will be indoors so if I need to refrigerate until pick up that's fine, just not sure if MMF will be Ok.
It will be fine. I have done it before without any problems.