In a medium saucepan, combine the drained beans, onion, garlic, and thyme. Add enough cold water to cover by 2 inches. Bring to a boil over high heat. Reduce the heat to medium-low and simmer for 20 minutes. Season with the salt and continue cooking until the beans are just tender, about 15 minutes more, depending on the dryness of the beans. Drain the beans, reserving 1/2 cup of the cooking liquid.
Return the beans and the reserved liquid to the saucepan. Add the cream and bring to a simmer over medium heat. Cook until slightly thickened, about 5 minutes. Stir in the butter, and season with salt and pepper.
These white beans scream comfort food! They are the perfect accompaniment to almost any main dish. Soaking the beans overnight and cooking them the next day gives the best texture and taste to the dish, but canned white beans can also be substituted for a last-minute version of this decadent side dish. Before serving, stir in chopped fresh herbs (rosemary would be good) for a savory twist.