For a baker, one of the most important ingredients is buttermilk. Buttermilk is commonly used in scones, biscuits, soda breads, and doughnuts. Buttermilk gives baked goods a richness, a mild tartness, and a consistency (due to its thickness compared to milk or cream) that is unrivaled. Storebought buttermilk, unfortunately, is not comparable to farm-fresh buttermilk. Buttermilk was traditionally made by churning heavy cream until the mixture separated into butter (solid) and buttermilk (liquid). If you would like to see the process firsthand, beat heavy cream until you get whipped cream. Then keep beating until you get butter. The liquid at the bottom of your bowl is buttermilk.
Store-bought buttermilk is actually skim milk that has been cultured by the addition of lactic acid, then pasteurized and homogenized. The flavor does not compare to dairy-fresh buttermilk. Upon reading Darina Allen's recipe for Irish Soda Bread, I was extremely jealous knowing that she likely had ready access to flavorful, rich, pungent buttermilk from her 100-acre organic farm in Ireland.