Black walnuts are a native American nut that has a strong, slightly bitter flavor. They are not always easy to find in the grocery, but you can substitute regular walnuts with equally good results. This bread can be frozen. As soon as possible after cooling, enclose bread in a plastic freezer bag, plastic wrap, or foil and seal well. Will stay fresh for two to three months. When ready to serve, simply remove the wrapped bread from the freezer and allow bread to stand, still wrapped, at room temperature until thawed. Or unwrap the bread and place on a baking sheet in a 350 F. oven for ten to fifteen minutes until thawed.