In large microwavable bowl, place 2 tablespoons of the butter. Microwave uncovered on High 30 to 90 seconds or until melted. Stir in flour; microwave 30 to 90 seconds longer or until thickened. Stir in cream, lemon juice, mustard, Worcestershire sauce and remaining 1 1/2 teaspoons salt. Microwave uncovered 1 to 2 minutes or until bubbling at edges. Stir in cheese. Mixture will be thick. Spread evenly over casserole.