This was posted on Facebook from marthastewart.com. I never have buttermilk In my fridge unless I know ahead of time that I will need it. Usually I just decide to make something that requires buttermilk & I have always added vinegar to milk to make a substitute. This short video discusses 4 different ways to make substitutions for buttermilk. Definitely worthwhile watching it
*** I use dry buttermilk powder when I don’t have buttermilk!
Here is a link to the video