Swiss chard is indeed a variety of beet (Beta vulgaris)selected for the greens rather than the root. The Romagnolis' Table suggests boiling leaves and stems, draining, and dressing with olive oil and lemon juice. We cook the stems about 2 minutes, add the leaves to cook for another 2 minutes. These are good even without any dressing, but oil and vinegar are good too.

For beet greens, I'd try eating some of the stems raw. If they are very tough and flavorless, then maybe they should be cooked separately, so they can be thrown out if they don't cook up nicely. Otherwise, treat as chard. We do.