In 4-cup glass measuring cup, mix broth, milk, mustard, thyme and pepper; set aside. In 4-quart saucepan, melt remaining 1/3 cup butter over medium heat. With whisk, stir in flour until smooth. Cook and stir 1 to 2 minutes or until mixture is smooth and bubbly. Gradually stir broth mixture into saucepan. Increase heat to medium-high; heat to boiling, stirring constantly. Boil and stir 1 minute; reduce heat to medium. Stir in cream cheese and Swiss cheese. Cook, beating mixture with whisk, until cheeses are melted and mixture is smooth. Remove from heat.