I like them just gently cooked in a little butter, with garlic, salt and pepper. But also like them added to curries, or a Chard Aloo etc. I find separating and cooking the leaf part from the chopped stems works better if you can be bothered, though they don't stay crisp. Steamed or boiled is good too, though a good bit of seasoning helps.
Sauteed with a little chopped bacon formed into a shallow nest and then an egg cracked into it, lid on and let it gently poach, yum!