This leafy green is almost the poster child of leafy greens, thanks to the calcium, potassium, and vitamins A, K, B6, and C it contains. Its slightly bitter flavor is good in salads, especially paired with something sweet like diced apples or dried fruit. You can also steam, stir-fry, or roast kale leaves and break them up into “chips.” Choose a bunch with leaves and stalks that are firm and deep green. Store up to five days in your fridge. Any longer and your kale will toughen.