JArthur wrote:

> Now this sounds pretty straight forward. But everytime I get down to
> about 8 tablespoons of butter left the entire batch in the mixing bowl
> turns into something resembling cottage cheese floating in a brown
> soup. I've tried using colder butter and warmer butter and same thing
> happened each time. Can somebody please tell me what I'm doing wrong?
>
> Oh there are a couple things I have noticed but I don't know if they
> mean anything.
>
> 1. I notice that no matter how light and fluffy I get the eggs, the
> foam always deflates when I start adding the butter.(I dunno if this is
> normal or not)
>
> 2. When the batch goes bad it happens suddenly rather than gradually.

It _sounds_ like you are using Alton Browns recipe, and based on that
assumption it sounds like you are adding the butter too soon at the end.
You have to really be patient with it & make sure you are adding the
small chunks of butter slowly and completely mixed in without any
leftover lumps.

You can read the transcripts here
http://www.goodeatsfanpage.com/Seaso...IcingTrans.htm to help
remind you of the important tips that are very important to buttercream
frosting success. here is an excerpt from that section of the
transcript that discusses this very problem that you seem to be having.

"Up to this point we've used our caramel-making skills, our
mayonnaise-making skills, and our cream-whipping skills. Time to give
our curd making skills a little bit of a flex. That means adding this
fat [butter] to this mixture very slowly, allowing each addition to
fully integrate before adding more. Basically, we're just gonna drop in
the butter, and we're gonna wait until there's no more physical evidence
of it being there before we add another one. Now this is going to go
pretty quickly at first, because there us a lot of residual heat there.
But as time goes by, it's going to take longer and longer before we can
add our next piece of butter. Oh, you think you can rush? Well do not be
tempted, or you'll end up frosting your cake with something that looks
[like a bowl full of icing with butter liquid at the bottom]. Yum."

I also believe the butter has to be room temperature, but you might want
to read the full transcript to make sure.