Parboiled Swiss chard requires cooking in boiling water and THEN sauteeing. (Whereas braised Swiss chard requires sauteeing and THEN cooking more thoroughly in water.)
You can use the stalks or not. But if you DO, then you can just leave them attached to the chard.
Boil a pot of water. Next, add the Swiss Chard and cook for just a few minutes, until the colors are vibrant. Carefully remove the chard from the water and drain completely.
Your chard is now parboiled and can be used in any way you'd like.
This technique is a wonderful way to keep the colors bright if presentation is important. Another reason to use this technique is if you're preparing a stir-fry -- you can parboil all the veggies first so they finish stir-frying at the same time. Or you can saute the Swiss chard in a bit of extra-virgin olive oil until tender.