While naturally sweet in flavor, walnuts have a bitter outer skin. So right before using them I remove it. First, preheat the oven to 350°F. Spread the walnuts on a large baking sheet and toast for 8 minutes, stirring halfway through the cooking. Remove from oven to cool. Transfer walnuts to a sieve and, holding the sieve over the sink, rub the walnuts against the wire until the skins loosen and fall off. Set aside to completely cool. While you will get the freshest most flavorful walnuts by purchasing them in the shell and cracking them before using, it can be time consuming. So I buy shelled, whole walnut halves and store them in the freezer.