How to Make It
In a large nonreactive saucepan, combine 1/4 cup of the oil with half of the onions, the sausage meat and 2 cups of the Concentrated Tomato Sauce. Cook over moderately high heat, stirring often, until bubbling. Stir in 2 cups of water, cover partially and cook until thick, about 1 hour. Season with salt and pepper.
Meanwhile in a large deep skillet, heat 1/4 cup of the oil. Add the remaining onion and cook over moderately high heat, until softened. Add the veal and cook over high heat, stirring to break the meat apart, until it just begins to brown, about 10 minutes. Add the remaining 3/4 cup of Concentrated Tomato Sauce, the sugar and 4 cups of water and bring to a boil. Cover partially and cook over moderately low heat until thick, about 1 hour.
Preheat the oven to 375°. In a large pot of boiling salted water, cook the fennel bulbs until tender, about 8 minutes. Using a slotted spoon, transfer the fennel to a work surface. Cut out the cores and discard; cut the bulbs into 1/4-inch dice and transfer to a large bowl. Bring the water back to a rapid boil. Add the pasta and cover partially until the water just returns to a boil. Add the pasta and cover partially until the water just returns to a boil, then uncover, stir and cook until al dente. Drain the rigatoni; add it to the bowl.
In a small bowl, toss the bread crumbs with the remaining 1 tablespoon of oil. Generously butter two 2-quart soufflé dishes. Coat the dishes with the bread crumbs, tap out any excess and reserve.
Add both of the sauces to the rigatoni along with the grated cheese and the fennel fronds; stir well and season with salt and pepper. Spoon the pasta into the soufflé dishes and pack down lightly. Sprinkle the remaining bread crumbs on top and bake for about 30 minutes, or until golden and the sauce is bubbling. Transfer the dishes to a rack and let rest for 15 minutes. To unmold, place a large plate over each soufflé dish and invert; remove the soufflé dish. Serve immediately, cut in wedges.