I followed a recipe for a caramel swiss meringe buttercream. 5 eggwhites and 1 1/2 c sugar whisked in mixing bowl over simmering water until 150F. Whip in stand mixer until doubled in volume and sides of the bowl are cool to the touch. Add 1# butter, softened, 1T at a time, then add salt, vanilla and 1/2 cup caramel. I have made swiss buttercream before with no problem. This time, the frosting never set. It was soupy. It never curdled when I added the butter in, never got thick. It tastes great, but no chance of being able to pipe it unless it hardens. I put it in the fridge hoping it will harden to pipe. Any chance this will happen? And, if it does harden enough to pipe, will it melt if left out? I want to frost a cake and cupcakes with it, and don't want to have to worry about refrigerating them once arriving at the party.
Was the butter too warm? The egg whites and sugar whipped up beautifully. Were they still too warm when I started adding the butter?