Substitute long fusilli or fettuccine if you can't find bucatini. Dried porcini mushrooms and truffle oil supply rich earthiness. Use leftover truffle oil to drizzle over pizzas, polenta, or salad greens.
1. Rinse porcini thoroughly. Combine porcini and 2/3 cup boiling water in a bowl; cover and let stand 30 minutes. Drain in a sieve over a bowl, reserving 1/4 cup soaking liquid. Chop porcini.
2. Cook pasta with 1 tablespoon salt in boiling water 10 minutes or until al dente; drain in a colander over a bowl, reserving 1/4 cup cooking liquid.
3. Heat oil in a large skillet over medium-high heat. Add shallots, mushroom blend, and garlic; sauté 5 minutes, stirring frequently. Stir in porcini, sherry, and 1/4 teaspoon salt; cook 1 minute or until liquid evaporates.
4. Finely grate 1 ounce cheese; crumble remaining cheese. Reduce heat to medium. Stir in pasta, 1/4 cup reserved cooking liquid, 1/4 cup reserved porcini soaking liquid, 1/4 cup grated cheese, cream, chopped sage, and pepper; toss well to combine. Drizzle with oil; toss. Place about 1 1/4 cups pasta mixture on each of 4 plates; top each serving with about 1 tablespoon crumbled cheese. Garnish with sage sprigs, if desired.