A dark-green leafy vegetable that belongs to the cabbage family and resembles kale. Oriental mustard greens are a milder tasting variety. Mustard greens are cooked before eating; steaming and sauteeing are common methods of preparation. The greens can be served with cheese or white sauce. Alternatively, the greens can be included in casseroles, omelets, or soups. Mustard greens provide (cooked, 1 cup) 21 calories; protein, 3.2 g; carbohydrate, 2.9 g; fiber, 2.9 g; calcium, 104 mg; iron, 1.7 mg; vitamin A, 424 retinol equivalents; thiamin, 0.06 mg; riboflavin, 0.09 mg; niacin, 0.61 mg.