Cook pasta according to package directions; drain. Return pasta to saucepan; cover and keep warm.
Meanwhile, in a large skillet heat oil and margarine over medium-high heat. Add garlic; cook and stir for 30 seconds. Add mushrooms, onion, and prosciutto. Cook for 4 to 5 minutes or until mushrooms and onion are tender, stirring occasionally. Remove from heat.
Add the pasta, spinach, the 1/4 cup Parmesan cheese, the salt, and black pepper to mushroom mixture; toss gently to combine. Divide the pasta mixture between 2 shallow pasta bowls or dinner plates. If desired, sprinkle with the shaved Parmesan cheese.