I have a recipe that asks for 100 ml of buttermilk. I wouldn't ordinarily buy buttermilk as it just another extravagance for baking (in my mind anyway), so could I just use ordinary milk and at the same quantity?

It wouldn't be quite the same, buttermilk is richer and has a different flavour. It depends on what you are making. These are things I have occasionally used in place of buttermilk. If you have some plain yoghurt you can mix half and half yoghurt/milk. Another alternative is to add 1 tablespoon white vinegar to 1 cup of milk and let it stand for 5 minutes.

Cheers,
Marnie

Gee, that's interesting Marnie. I will try the vinegar with the milk. It's for coffee cupcakes and the recipe also uses brown sugar so it must be quite a lovely rich taste.

can you do the same to replace yoghurt in a recipe?

It would depend what you were making Sue. It would probably be OK in baking but you might need to reduce the liquid a little as it isn't as thick as yoghurt.

I used buttermilk to replace yoghurt, when making naan at the weekend and that worked well. I use buttermilk in scones, without buttermilk I can't make scones to save myself.