(optional) If you think of it, you can soak the mung beans for several hours ahead of time to reduce their cooking time.
Heat oven to 350 degrees. Cut squash and sweet potato in half lengthwise, and place cut side down on oiled baking sheet. Roast in oven until tender (about 30 minutes), then remove and set aside to cool
If mung beans were presoaked, drain and rinse them. Place in medium pot with water and bay leaves. Simmer until tender (about 40 minutes with no soaking, 15-20 minutes with soaking). Drain, rinse, and set aside.
In large pot, saute onions and garlic in olive oil until translucent. Add celery and cook until tender.
When squash and sweet potato are cool enough to handle, scoop their flesh into the pot with the onion/garlic/celery mixture.
Add broth and bring to simmer.
When everything seems well cooked and tender, puree the mixture with a blender or immersion blender. Add more water if it seems too thick.
Return mixture to pot and add chard. Cook until chard is wilted.
Add mung beans and rosemary. Simmer to blend flavors.
When everything seems well cooked, turn off heat. Stir in parsley or other fresh herbs. Drizzle truffle oil over top of soup and stir in. Season to taste with salt and pepper.