How to Make It
In a large enameled cast-iron casserole, heat 2 tablespoons of the olive oil. Add the sausage and cook over moderate heat, stirring, until browned, 5 minutes; transfer to a plate. Add the fennel, half of the onions and the smashed garlic to the casserole and season with salt and black pepper. Cook, stirring, until the vegetables are golden and softened, about 10 minutes. Add the sausage, red wine, tomatoes and 2 cups of water and bring to a simmer. Cook over low heat until the sauce is thickened, 45 minutes.
Meanwhile, in a large saucepan, heat 2 tablespoons of the olive oil. Add the remaining chopped onions and cook over moderate heat, stirring occasionally, until golden and softened, about 10 minutes. Add the chopped escarole in batches, stirring until each batch is wilted before adding more. Add 1 tablespoon of the olive oil and the minced garlic and cook, stirring, until fragrant, about 2 minutes. Add the white wine and a pinch of crushed red pepper and season with salt. Cook, stirring occasionally, until the escarole is tender, about 40 minutes. Stir the escarole mixture into the sausage ragù.
In a large pot of salted boiling water, cook the pasta until al dente. Drain, reserving ½ cup of the pasta water. Return the pasta to the pot and add the reserved water, 5 cups of the ragù, the remaining 1 tablespoon of olive oil and the 1 cup of grated cheese. Season with salt, black pepper and crushed red pepper and toss to coat. Serve with additional cheese. Reserve the remaining ragù for later use.