Cannellini al Gratin

1. Soak beans in large bowl of cold water overnight. Drain.

2. Put beans in 6-qt. Dutch oven, and add enough water to cover by 2 inches. Tie together thyme and parsley sprigs, and add to pot. Pierce onion half with cloves, and add to pot. Add fennel fronds and stalks 
to pot with 6 halved garlic cloves. Partially cover, and bring to a boil. Uncover, reduce heat to medium-low, and simmer 35 to 40 minutes, or until beans are just tender. Drain beans, and reserve cooking liquid. Discard herb bundles, onion, and fennel. Wipe out Dutch oven for next step.

3. Preheat oven to 400°F. Heat 2 Tbs. oil in Dutch oven over medium-high heat. Add carrots and diced fennel, and season with salt, if desired. Cover, and cook 10 minutes, or until beginning to brown, stirring frequently. Add diced onion, season with salt (if desired), and cook, covered, 6 to 8 minutes, or until onion is soft and bottom of pan is browning, stirring occasionally. Add minced garlic, and cook 1 minute, or until fragrant. Remove pot from heat, and stir in vinegar, using spatula to scrape up any browned bits of onion stuck to bottom of pot. Add beans, chopped thyme, 
2 Tbs. chopped parsley, 1/2 cup Grana Padano, and 1 1/2 to 2 cups bean cooking liquid. (Liquid should come to about 1 1/2 to 2 inches below top of beans; add more if necessary.) Stir well to combine.

4. Combine breadcrumbs, remaining 1 Tbs. chopped parsley, and remaining 1/4 cup Grana Padano in small bowl. Drizzle remaining 1 Tbs. oil into crumb mixture, and combine to moisten breadcrumbs. Spread breadcrumb mixture over bean mixture. Bake gratin, uncovered, 40 to 45 minutes, or until top is browned and juices have bubbled down below surface, leaving brown rim around edge of crust. Cool at least 20 to 25 minutes to allow beans to finish absorbing juices. Serve warm.