If using dried beans: The night before, soak the beans in a large bowl with water to cover by at least 2 inches. Cover and refrigerate overnight.
The next day, drain the beans, rinse them well, and place them in a large stockpot. Add twice as much water as you have beans, bring to a boil, lower the heat, and simmer uncovered for about 45 minutes, until the beans are very tender. Skim off any foam that accumulates.
Meanwhile, heat the olive oil in a large pan or Dutch oven over medium heat. Add the fennel and carrots and sauté for 8 to 10 minutes, stirring occasionally, until tender.
Add the garlic and cook for 1 minute more. Drain the beans and add them to the vegetables. (If you are using canned beans, add the beans and the liquid from the can at this point).
Add the chicken stock, sage, rosemary, salt, and pepper and simmer, stirring occasionally, for 12 to 15 minutes, until creamy.
Stir in the Pecorino, season to taste, and serve hot.