Combine the onion, cider, chicken stock, and salt in a large pot and bring to a boil over medium-high heat. Reduce the heat to medium and add the chard and kale. Cover the pot and simmer for 10 minutes. Check the greens for tenderness, stir them, and add a little more salt. Re-cover the pot and cook until the greens are fully tender, about 4 minutes more.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.