How to Make It
In a large enameled cast-iron casserole, heat the olive oil until shimmering. Add the veal and pork and cook over moderately high heat, stirring occasionally, until most of the liquid has evaporated and the meat is nearly cooked through, 6 to 8 minutes. Add the wine and cook over moderate heat, scraping up any browned bits from the bottom of the casserole, until evaporated, about 3 minutes.
Add the half-and-half and chicken stock to the casserole, then stir in the thyme, rosemary, sage, bay leaf, garlic, pink pepper, crushed red pepper, nutmeg and a generous pinch each of salt and black pepper. Bring just to a simmer. Cover and cook over moderately low heat, stirring occasionally, until the sauce has thickened slightly and the meat is very tender, about 2 hours.
Meanwhile, in a medium skillet, cook the bacon over moderate heat, stirring, until the fat has rendered, about 5 minutes. Add the onion, mushrooms and celery root and cook, stirring, until the soffritto has softened, about 7 minutes.
Stir the soffritto into the Bolognese sauce, cover partially and cook over moderately low heat, stirring occasionally, until the sauce has reduced just slightly, about 25 minutes longer. Discard the thyme, rosemary and bay leaf. Season the Bolognese sauce with salt and black pepper and keep warm over very low heat.
In a large pot of salted boiling water, cook the pappardelle until al dente. Drain, reserving 1/4 cup of the cooking water. Add the pasta and cooking water to the Bolognese sauce and toss over moderate heat until the pasta is well coated, about 2 minutes. Transfer the pasta to a large, shallow bowl and serve right away, passing Parmigiano-Reggiano at the table.