Thaw shrimp, if frozen. Rinse shrimp; pat dry with paper towels. In a Dutch oven, cook pasta according to package directions; drain. Return to Dutch oven; cover and keep warm.

Meanwhile, in a small bowl, combine 3/4 cup broth, sherry or additional broth, lemon juice, crushed red pepper, and salt; set aside. In a large skillet, cook shrimp, 1/4 cup pine nuts and garlic in hot oil over medium heat 2 to 3 minutes or until shrimp are opaque. Remove shrimp mixture from skillet. Add mushrooms and butter; cook 3 minutes until almost tender. Carefully add broth mixture to skillet. Bring to boiling; reduce heat. Boil gently, uncovered, for 5 minutes. Return shrimp mixture to skillet; heat through.

Add shrimp mixture and spinach, if you like, to pasta; toss to coat. Transfer to a serving bowl. Sprinkle with Asiago cheese and toasted pine nuts, if you like. Makes 4 servings.