Cook farfalle according to package directions. Drain well.
Meanwhile, in a large skillet, cook and stir onion, mushrooms, and garlic in hot oil over medium heat for 2 to 3 minutes or until mushrooms are nearly tender. Stir in spinach, thyme, and pepper; cook for 1 minute or until heated through and spinach is slightly wilted. Stir in cooked pasta; toss gently to mix. Sprinkle with cheese.