1Marinate the chicken: In a bowl large enough to hold the chicken thighs, combine 2 garlic cloves, the rosemary, 1/2 teaspoon thyme, and the vinegar. Add the chicken; toss to coat. Cover; refrigerate 1 to 2 hours.
2Preheat the oven to 375°F, with the rack in the upper third. Drain the beans, and place them in a large stockpot with the carrots, celery, onion, remaining 3 garlic cloves, bay leaf, sage, and remaining teaspoon thyme. Fill with enough cold water to cover by about 4 inches; bring to a simmer over medium-high heat. Reduce heat to medium-low; cook, stirring occasionally, until the beans are tender, 1 1/2 to 2 hours.
3Transfer the bean mixture to a colander set over a bowl, reserving the cooking liquid; let cool slightly. Puree half the mixture in the bowl of a food processor fitted with the metal blade. With the motor running, pour in about 1 cup reserved cooking liquid until thick and smooth. Return to the pot with the remaining bean mixture. Add the salt; stir to combine.
