Sure, today kale is the glamour-puss of the winter greens crowd. But it wasn't so long ago that that crown belonged to the chards. And though fashion may have moved on, they do still have a lot to recommend them.
First cousin to the beet, chards (there are several) are one of the best cool-weather cooking greens. You'll usually find them in three variations – green, which has white stems and a fairly mild flavor; red, which closely resembles beet greens in looks and taste; and rainbow, which is not really a genetic variety, but a mix of types that includes both red and white, plus shades of pink and gold (sadly, beautiful as they are raw, the color dulls with cooking).
The term "Swiss chard" generally refers to any of those three. All of them have fairly crisp, ridged stems and thick fleshy leaves that are, frankly, unpleasant raw but become absolutely wonderful when cooked.
The secret to cooking chards – as with most winter greens – is to cook them low and slow. They'll lose their crispness and then become definitely tender. But if you push them just a little further still, you'll find that they have become terrifically earthy and sweet. Patience is a virtue; it might take as much as 45 minutes over very low heat.
You can short-cut the cooking a little by blanching the chard in rapidly boiling salted water before sauteing it. Just be sure to squeeze out all the excess moisture before you add the greens to the pan.
Because the stems are so much denser than the leaves, they require longer cooking. Generally, you can start cooking the stems by themselves and then, just as they're beginning to become tender, add the leaves.
How to choose: Don't worry so much about the leaves – you'll get a lot more clues about the freshness of the chard by looking at the stems (they seem to wilt before the leaves do). The stems should be firm and crisp. Examine the cut end – it should be somewhat moist and fresh-looking, with minimal darkening.
How to store: Keep chard tightly wrapped in a plastic bag in the crisper drawer of the refrigerator. Properly stored, it'll last a week or so. One thing: Chard often seems to be sandier than some other greens, so clean it thoroughly by covering it with water in the sink and then giving it a good shake. It's important that you do this right before cooking rather than before you stick the chard in the fridge – excess moisture is the great enemy of almost all fruits and vegetables.