Originally Posted by costumeczar
It's best used to cover cakes when it's freshly made, if you put it in the fridge you ahve to let it warm to room temp and rewhip before using it, and it's never as good to cover cakes with once you've done that. I do that for fillings all the time but I wouldn't use a meringue buttercream that had been refrigerated to cover a cake.
This is true to a point...
I've been using SMBC for years now as I can't bear the (to me) over-sweet grainy icing sugar/butter mix. If you stick it in the fridge it is a pita to use without a bit of reworking. 9 times out of 10 in fact I'll find mine turns into a curdled mess when back at room temperature.
If you're using it from the fridge or freezer (I love freezing this stuff - no more waste!), let it get back to room temperature and then give it a cursory beating. Now take out a good 1/3 of the buttercream and melt it completely in the microwave. Pour the melted mess onto your (probably) curdled mess and start beating, either by hand or with an electric mixer. After a few minutes it will come together into a beautifully glossy smooth buttercream. Promise
I find this a nicer finish that when I've just made it (it seems to reduce air bubbles, particularly if I just re-work it by hand), so I quite often make it a few hours ahead of time, leave it on the worktop or in the fridge (at the moment with no heating in the kitchen they're pretty much one and the same), then do the melting/beating to bring it to the smooooth finish which is lovely for cupcakes. I'm in the UK so we don't really do big cakes in buttercream, we're more sugarpaste inclined over here, so when I'm using for a layered cake I just use it fresh if I have it.
Oh, and I'm always in awe of how smooth you can get your buttercream cakes in the US - is that due to using the crusting type? I have to get smooth finishes in order to use the sugarpaste on top of it, which I do using a warm metal edge, but there's always a few bits I'm not entirely pleased with! Luckily mine gets covered