How to Make Buttermilk
How to make buttermilk from milk is a topic that's come up over again. There are a lot of recipes, an article written on this subject. They all give different techniques, tips, and recipes. It's not an easy task, as the resulting milk will be different than what you have in the fridge.
1 cup Milk
Put the vinegar in a glass measuring cup, and add enough milk to make 1 cup of total liquid.
Stir to combine and allow to stand for 10 to 15 minutes (mixture will rotate).
See the full directions on my site