Asparagus-Mushroom Orzotto

Heat olive oil and butter in large saucepan over medium heat. Add onion and sauté 10 minutes, or until soft. Add garlic, and sauté 2 minutes. Add asparagus and mushrooms, and sauté 5 to 7 minutes, or until mushrooms start to release their juices. Add 1/2 cup orzo and cook 3 to 5 minutes, or until lightly browned. Add remaining orzo, and cook 3 minutes more, or until all pasta bits are browned. Stir in 1/2 cup vegetable broth, parsley, and thyme, and simmer 2 to 3 minutes, or until orzo has absorbed all liquid, stirring often. Continue adding broth to orzo 1/2 cup at a time until all liquid is absorbed and orzo is al dente. Remove from heat, and stir in Parmesan, if desired. Serve with Osso Buco.