Mustard greens are the greens of the mustard plant (shocking!). The leaves have a sharp, bright flavor that may just remind you of mustard seeds at their greenest and most piquant. You can mellow the flavor by blanching them in salted boiling water for a minute or two, draining, and then using. Or, sauté them as-is for a sharper flavor. While any hearty cooking green works in Greens with Mustard Seeds, using mustard greens has a delicious – and conceptual – appeal.