Buttermilk substitute ?

[FatSatsumaStuffedIntoAStocking]

I know there's an easy-to-make substitute but I just can't remember it. Something like yoghurt plus lemon juice?? Please can someone put me out of my misery?

50% yogurt and 50% milk works with muffin recipes

Thank you! It's for a cornbread topping for chilli (Nigella Feast) but I'm sure it will do the job. What kind of yoghurt?

You can also plain natural yoghurt on it's own - if it's a runny one. Or soured cream. Or add lemon juice - or even white vinegar - to milk, and leave it for 5 ish mins.

Thanks Hazel - sounds like runny yog will do

I use live yoghurt and it works perfectly.