No matter how much I beat it, whether with my whisk or with my Kenwood beater, it just started to get more and more separated. I started to panic a bit...then decided to try a second time from scratch.
I ended up pouring off the liquid, beating the lumpy mess until it started to look a bit more smooth, then I added the liquid back in slowly while beating it.
I resigned myself to the fact that the cupcakes were probably to going to turn out a disaster but it was good to know now rather than wait until the night before the baby shower to realise this!
I combined the lumpy buttermilk mixture with the dry ingredients and stirred in the red food colouring. Amazingly, as I lightly folded the ingredients together, the mixture became smoother and smoother! Woo!