Buttermilk Cabbage Soup With Black Walnut "Pesto"

Cabbage is a green you can keep in the root cellar deep into the winter, and it is often sliced thin and sautéed in butter or bacon grease as a sturdy side for a cold-weather supper. This soup pairs it perfectly with tangy buttermilk and the fragrantly earthy black walnuts that fall in abundance in the autumn. Black walnuts are a bear to get to, their outer husks staining hands a deep purplish black, the inner shells so hard that it breaks the nut meats inside to crack them. But they are so beloved and flavorful that mountain families would spend long winter evenings peeling, cracking, and picking black walnuts by the fire. If you don’t have or don’t like black walnuts, you can make the “pesto” with pecans. It will be great, but just different.