However, if you're completely out of buttermilk and have absolutely no idea how to substitute with sour cream, the general rule of thumb is to combine the sour cream with a liquid (usually milk ...

As this is not readily available or always to hand, I have resorted to adding a little vinegar to milk. What difference does buttermilk make to the recipe? What can be used as a substitute?

if you don't have a ready supply of buttermilk ... You can usually also use plain yoghurt as a substitute, but may need to thin it down with some milk so that it is a pourable consistency.

if you don't have a ready supply of buttermilk ... You can usually also use plain yoghurt as a substitute, but may need to thin it down with some milk so that it is a pourable consistency.