In a saucepan combine soup, milk, onion, and mustard; cook and stir till heated through.
Remove from heat; stir in cheese till melted.
Pour 1 cup of the soup mixture into a 10x6x2-inch baking dish.
Carefully break eggs atop soup mixture in baking dish.
Spoon remaining soup mixture around eggs.
Stand bread halves around baking dish edges, crust side up.
Bake, uncovered, in a 350° oven about 20 minutes or till eggs are set to desired doneness.
Sprinkle with parsley.
To serve, spoon soup mixture over eggs and bread slices.