This is a thick, old-fashioned New England Buttermilk which can be made with skim or whole milk.
The amount of character (acid, flavor, texture) can be controlled by increasing or decreasing time and/or temperature.
Each packet sets 1-2 quarts of milk and makes 1-2 quarts of buttermilk. We recommend using 1qt. If you would like to use 2qts, simply give it a little more time to set.