Here's how to make cultured buttermilk:
MAKING CULTURED BUTTERMILK FROM SCRATCH
Allow a cup of filtered fresh raw milk to sit covered at room temperature until it has clabbered (usually several days).
Place 1/4 cup of the clabbered milk in a pint mason jar, add a cupof fresh milk (does not have to be raw at this point), cover, shake to mix, allow to sit at room temperature until clabbered.
Repeat this transfer of sub-culturing several more times until the milk dependably clabbers in 24 hours. Taste a small amount to confirm that it is tart, thickened, and has no off flavors.
To then make a quart of buttermilk with this culture, add 6 ounces of the buttermilk to a quart jar, fill with fresh milk, cover, shake to mix, allow to sit at room temperature until clabbered.
Refrigerate.
Here's how to make an easy substitute for buttermilk:
To make pretend buttermilk, add 1-3/4 tablespoons of cream of tartar to a cup of milk, or add a tablespoon of lemon juice or white vinegar to a cup of milk and let it stand for 5 to 10 minutes. In many baking recipes, you can also just use plain yogurt or sour cream instead of buttermilk.
~Lisa