1. Preheat oven to 400°.
2. Cut top off garlic head. Place in a small baking dish, and drizzle with 1 teaspoon oil; cover with foil, and bake at 400° for 45 minutes. Remove dish from oven. Add 1/2 cup boiling water to dish; cover and let stand 30 minutes. Separate cloves; squeeze to extract garlic pulp into water. Discard skins. Mash garlic pulp mixture with a fork, and set aside.
3. Combine remaining 2 cups boiling water and dried mushrooms in a bowl; cover and let stand 30 minutes. Rinse mushrooms; drain well, and roughly chop. Set aside.
4. Cook pasta according to package directions, omitting salt and fat.
5. Heat remaining 2 tablespoons oil in a large nonstick skillet over medium-high heat. Add sage to pan; sauté 1 minute or until crisp and browned. Remove from pan using a slotted spoon; set aside. Add cremini mushrooms, salt, and pepper to pan; sauté 4 minutes. Add garlic mixture, chopped mushrooms, and broth to pan; cook 5 minutes or until liquid is reduced by about half. Grate 1 1/2 ounces cheese. Stir pasta and grated cheese into pan; cover and let stand 5 minutes. Thinly shave remaining 1/2 ounce cheese; top each serving evenly with cheese shavings and sage leaves.