Don’t want a fridge full of different milks, yogurts and cream? The good news is, these are easy to swap. If you can’t find buttermilk, use yogurt or milk with a squeeze of lemon juice to provide the acid. Crème fraîche and soured cream are largely interchangeable, and even a dollop of Greek yogurt would work instead – try it in mash. One thing not to swap: single cream will not whip or thicken like double cream does, so use it for pouring only.