I made a french buttercream and froze it last week. So, I took it out of the freezer today and put it in the fridge. In a rush, I popped it in the microwave tonight on defrost and melted it (on accident). Put it back in the fridge. It looks almost curdled. I tried beating it. No change. Is there any way I can save it? (If not, I have some vanilla leftover - this was the mocha. It's for cupcakes for my friend's bridal shower.)

The only ingredients in it are egg whites, granulated sugar, butter, vanilla extract, cocoa powder and kahlua.

Does it look like it soured? It has like little lumps? If so, pop it in the microvawe again for few seconds (depends how big batch you have, I put 4 cups for about 20 sec.) not to melt it but warm it. It will loosen up the curds - whip it right away..... Well this work with mine butter cream and it has almost the same contents. The thing is why it curds is the temperature is not same through the whole buttercream, and when u whip it it get curds. So warming it up loosens it.... Do you get what I mean. Just try it, I guess u have nothing to loose. Just please DO NOT melt it again. Just warm up.