How to Make It
In a food processor, pulse the onion, carrot, celery, parsnip, turnip and king oysters until finely chopped. In a large pot, heat the oil. Add the vegetables, season with salt and pepper and cook over moderate heat until softened, 20 minutes.
In a bowl, cover the porcini with 1 1/2 cups of boiling water; let stand until softened. Drain, reserving 1 cup of the water. Rinse and chop the porcini, add to the vegetables and cook until fragrant, 10 minutes. Add the wine, rind and red pepper; cook until the wine evaporates. Add the reserved porcini water, cover partially and cook over low heat, stirring, until thick, 25 minutes. Add the cream, rosemary and 1/4 cup of grated cheese and simmer for 5 minutes. Discard the rind.
Add the warm pasta, butter and 1 cup of water to the sauce and toss, stirring until the pasta is well-coated. Serve.