Pappardelle with Mushrooms

INGREDIENTS

• 1/2 cup dried porcini mushrooms (about 1/2 ounce)
• 2/3 cup boiling water
• 8 ounces uncooked pappardelle pasta or bucatini
• 3 1/4 teaspoons salt, divided
• 1 tablespoon olive oil
• 1/4 cup finely chopped shallots
• 2 (4-ounce) packages exotic mushroom blend, sliced or coarsely chopped
• 2 garlic cloves, minced
• 2 tablespoons dry sherry
• 2 ounces Parmigiano-Reggiano cheese, divided
• 1/4 cup heavy whipping cream
• 1 teaspoon finely chopped fresh sage
• 1/2 teaspoon cracked black pepper
• 1 teaspoon truffle oil
• Sage leaves (optional)