Buttermilk is almost to easy to make.  If you use buttermilk a lot in cooking then making your own can save you a little money. The process to make sour cream is the same as buttermilk with the same bacteria culture used.  The only difference is that instead of milk you use cream.

Ingredients:

• Buttermilk culture (you can use store-bought buttermilk as long as it has live cultures in it)
• 1 gallon whole milk for butter milk or cream for sour cream

Heat the milk for buttermilk or cream for sour cream to 185 degrees, and hold for 45 minutes. (For added body you can add 1/2 cup of non-fat powdered milk before heating). If you can, please do this in a double boiler.  It is extremely easy to scorch the bottom of the pan.  I have done it more than once when I first started making cheeses

Cool the milk or cream down to 77 degrees and add 1/8 tsp. of culture to it.  If you add the culture before it hits 77 you will cook your bacteria.  Stir gently until dissolved. If you are using store-bought buttermilk with a live culture use ¼ of a cup

It is recommended to hold at 74-77 degrees for a minimum 16 to 18 hours. But I use normal room temperature of 72 degrees for it to incubate (love that word, reminds me of the movie Aliens) At room temperature it takes it about 20 hours to thicken up and be ready.  When it is done refrigerate and use as you like

If you like to make Labneh (yogurt cheese) then you can make a similar cheese from butter milk.  Line a colander with a large, sterilized handkerchief and pour your buttermilk into it.  Then tie the corners together and let it hang to drain out all the whey for around 12 hours.  After it is drained scoop into a sealed container and use as you would cream cheese.  The flavor you get from this is amazing on a bagel sandwich.