In 2-quart saucepan over high heat, heat 1 cup chicken broth and garlic to boiling. Stir in broccoli, carrots, pepper, and onion. Reduce heat to medium. Cover; cook 5 minutes until vegetables are tender-crisp. In cup, stir together cornstarch and remaining chicken broth until smooth, stir into vegetable mixture. Cook until mixture boils and thickens, stirring constantly. Gently stir in tofu; heat through. Serve over spaghetti. Sprinkle with cheese. Serves 4-5.