In a dutch oven, place the pancetta and cook over medium heat until most of the fat is rendered. Add the beans, 1 clove garlic, and half of the parsley and cook over medium-high heat, stirring occasionally. Cook for 5 minutes, until the onion is softened, then add the tomatoes, and salt and pepper, to taste.
In a separate skillet, heat 1/4 cup oil over high heat and add the mushrooms. Cook over very high heat until they begin to get browned and crisp, then add 1 clove garlic and a pinch of parsley. Remove from heat and set aside.
In a large bowl, combine the ground veal, pork, grated cheese, egg, salt, and pepper, to taste, and, once they have cooled, the cooked mushrooms. Mix these ingredients well and divide evenly among the slices of veal, placing a portion in the center of each slice. Season with salt and pepper, and roll each slice up, securing with butcher's twine. Dust each roll with flour.
In a separate skillet, heat the remaining olive oil over high heat and add the rolls, working in batches to avoid overcrowding the pan. Brown the rolls on all sides, then add to the simmering bean and tomato sauce, and simmer for 20 minutes. Season the sauce with salt and pepper and serve the rolls with sauce drizzled on top.
Recipe copyright Mario Batali, 2002. All Rights Reserved.