Put the drained beans in a large saucepan and add water to cover the beans by 3 inches. Bring to a boil, cover, and simmer until very tender, 1 to 1 1/2 hours. Meanwhile, heat the oven to 400°F. Cut off the top third of the garlic head to expose the cloves. Coat the cut side with the olive oil, wrap the garlic loosely in foil, set on a baking sheet, and roast until soft, about 1 hour.
Drain the cooked beans; put them in a food processor. Squeeze about 8 of the roasted cloves of garlic into the bowl. (The rest of the garlic will keep, wrapped, for about a week in the refrigerator.) Add the thyme and half of the warmed cream and purée. Add just enough of the remaining cream while pulsing until the purée is the consistency of mashed potatoes. Season with salt and pepper.
nutrition information (per serving):
Photo: Ben Fink