Freshly ground pepper Cooked spaghetti, linguine -or penne Pour 1/4 cup of the broth into a small bowl or cup, and stir in the cornstarch until dissolved. Set aside. In a medium saucepan, bring the remaining broth to a boil over moderate heat. Add the vegetables and simmer until tender-crisp, about 3 minutes. Stir in the broth-cornstarch mixture, the yogurt, Parmesan, and herbs, and simmer just until thick, 1 to 2 minutes. Pour the sauce over cooked pasta. Season to taste with black pepper.