Hi prchick. I love questions that make me think before I type. I had a pretty good idea what the problem was but first I wanted to read the recipe and then think about what may be happening. So here's my shot at helping you figure out your problem.
First we have to look at your substitution. The recipe calls for:
1/2 cup unsalted butter,softened.
1/2 cup Blue Bonnet margarine, (assumed softened)
So let's compare butter and margarine.
Butter fat/oil content = around 35% Margarine fat/oil content = around 80%
(you see where I'm going with this?)
You introduced about 45% more fat/oil than the recipe asked for by substituting margarine for butter. That is why you ended up with the 'oil and water' problem because that is exactly what it was. There's also the fact that all margarine is salted (which is why using Crisco instead of margarine is a better recommendation).
If you are looking for a substitution for butter try using applesauce. Although I haven't actually tried this trick I have heard and read to do this from many different cook books and fellow bakers.
Please let me know if this helps at all or if I'm totally off base
Hi! I need help. I did the white chocolate frosting recipe and followed it perfectly but the frosting didn't mixed well, it was like trying to mix oil and water with other stuff in it. Does anyone knows what I did wrong? I used good quality products except insted of butter I used Blue Bonnet it's compost of oil spread.