Preheat oven to 350~F. degrees. Melt butter in large saucepan over medium low heat. Whisk in flour and stir 3 minutes. Gradually whisk in broth and milk. Reduce heat, simmering until thick, about 10 minutes. Blend in lemon juice and seasonings. Combine cooked noodles and half the sauce, tossing gently to blend. Place in the bottom of a buttered 2-quart casserole. Top with chicken and remaining sauce. Combine Parmesan cheese and paprika, sprinkle over casserole. Bake until bubbling and golden brown, about 30 minutes. Serve hot.