How to Make It
Place beans in a Dutch oven. Add water to cover by 2 inches; stir in bay leaves. Bring to a boil; boil 1 minute. Remove from heat; cover and let stand 1 hour. Return pan to heat over high (do not drain beans or refresh water); bring to a boil. Reduce heat to medium-low; simmer until beans are almost tender, about 30 minutes. Drain beans; discard bay leaves. Wipe pan dry.
Preheat oven to 300°F.
Heat 1 1/2 tablespoons oil in pan over medium-high. Add chicken; cook, stirring occasionally, until browned, about 8 minutes. Add sausage; cook, stirring occasionally, until browned, about 5 minutes. Remove chicken and sausage. Add onion, carrots, and celery; sauté 5 minutes. Add thyme, tomato paste, and garlic; sauté 2 minutes. Add wine; cook 1 minute, scraping bottom of pan to loosen browned bits.
Add tomatoes, stock, salt, pepper, beans, chicken, and sausage to pan; stir gently to combine. Cover and bake at 300°F 1 hour. Remove pan. Increase oven temperature to 425°F.
Scoop out 1 cup bean mixture, avoiding chicken or sausage. Mash with a fork; stir into chicken mixture.
Place baguette in a food processor; process until coarse crumbs form. Add cheese, parsley, and remaining 2 tablespoons oil; pulse to combine. Sprinkle breadcrumbs over cassoulet. Bake, uncovered, at 425°F until topping is crusty, 15 to 20 minutes. Let stand 5 minutes before serving.
Slow Cooker Method - Place beans in a 6-quart slow cooker. Proceed with step 3, substituting a skillet for the Dutch oven. Add chicken mixture and onion mixture to slow cooker. Omit step 4. Add tomatoes, stock, salt, pepper, and 1 2/3 cups water. Cover and cook on LOW until beans are tender, 7 to 8 hours. Omit step 5. Make breadcrumb mixture as directed in step 6; toast in a skillet over medium-high about 5 minutes. Sprinkle on cassoulet.