Cut the stems of chard into 1-inch lengths; slice the green chard leaves into 1/2-inch-wide ribbons. Cut mushrooms in half, cut carrots in half lengthwise, remove the strings from snow peas, and cut onions into 1/2-inch lengths.
In a 5-quart Dutch oven, heat butter with oil over moderately high heat. Add the green onions and saute for 30 seconds. Stir in the chard stems, mushrooms, carrots, garlic, water and frozen lima beans. Bring to a boil, stirring to thaw the beans. Reduce the heat to low, cover, and cook until the carrots are almost tender, 8 to 10 minutes.
Add the chard leaves and snow peas to the vegetable mixture. Continue cooking until the vegetables are crisp-tender, about 4 more minutes. Season the mixture with salt and pepper. Spoon the mixture into a bowl, sprinkle it with parsely, and serve immediately.