1. Cook onions in butter in saucepot on medium heat 30 to 35 minutes or until light golden brown, stirring occasionally.
2. Stir in beef and chicken broth, sherry, thyme and mustard. Bring to a boil on medium-high heat; reduce heat to medium-low. Simmer, uncovered, 20 minutes.
3. Meanwhile, preheat salamander or broiler. Place bread on baking sheet. Broil 1 minute or until light golden in color, turning over half way through broiling. Divide cheese and ham evenly on bread. Broil 1 to 2 minutes or until cheese is melted.
4. Divide soup evenly between 6 bowls. Top each with 2 slices bread and serve.
Nutritional information per serving: Calories 622; Total Fat 17g; Saturated Fat 9g;