Mix 2 pounds of shelled pecans, English walnuts, and black walnuts in whatever combination, but with no more than ⅓ pound of the black. My favorite combination is 1 pound pecans, ⅔ pound walnuts, and ⅓ pound black walnuts. Grind the nuts in small batches in a nut grinder or in a food processor fitted with the metal blade, working in quick bursts, until they are evenly ground. Do not blend them too long, or they will become oily. Store what you don’t use immediately in airtight containers in the refrigerator. You can freeze nuts, but they lose both flavor and texture when thawed. If you cannot find black walnuts at your grocer’s or your local natural foods store, Hammons Black Walnut Emporium in Stockton, MO, provides all kinds of black walnut products: www.black-walnut.com (800-429-6887).