The main changes was to add 2-3 Tablespoons of Worcestershire sauce. I also increased the herbs to 1 teaspoon each, and added extra broth as it thickened.
I made this in a 13" x 9" pan. I loaded it with Gouda cheese (I think I will use regular Swiss the next time) until it was melted, browned and crusty. One problem was the melted cheese spread too much and it was difficult to see where each chicken breast ended. As I served it, the cheese slid off, much like when you take a cheesy slice of pizza. I think I might try cooking them in individual au gratin baking dishes. I think it will keep all the cheese for each serving in one place and make for a nicer presentation. But I have to buy them first. I have 8 French onion soup dishes, but they are round and won't quite hold a chicken breast, unless I cut it into pieces.