So I found this great recipe for Chocolate Buttercream but it has milk in it. Doesn't that require it to be refrigerated??

No..Once it is mixed with all the icing sugar and cocoa it pretty much is good to leave out.The sugar content will look after any spoilage.

Thank you - what do you mean the sugar content will look after any spoilage? Thanks

There is so much sugar in the icing it basically absorbs into the fat of the milk not allowing the spoilage that you may get if you leave milk in the fridge too long and it goes sour.

Thank you very much!! =)

Sugar is hygroscopic (water absorbing) so it controls the water activity of liquid ingredients used in your American b/c recipe. (Will only work when amount of liquid is small and amount of sugar is large.)

Water activity & microbial growth:
(Prolonging Bakery Product Life.)

http://tinyurl.com/6fbkcz

WJ Scott in 1953 first established that it was water activity, not water content that correlated with bacterial growth:

http://tinyurl.com/bmsato

Formulating for increased shelf life:
(Decreasing water activity results in hostile environment for bacteria.)

http://tinyurl.com/csu2b9

HTH

Thanks Jan for the scientific explanation...