Lightly grease a 9X13-inch baking dish with cooking spray and preheat the oven to 350 degrees. In a bowl, combine the bread crumbs and melted butter. Set aside.
Lay the cut chicken breasts in a single layer in the 9X13-inch dish. Layer each chicken breast with two slices of ham and top with slices of Swiss cheese, layering across the chicken breast to make sure the entire chicken breast is covered with ham and cheese. Sprinkle the bread crumbs over the top of the chicken.
Bake the chicken for 30-35 minutes, until the chicken is cooked through completely, the cheese is bubbling and the bread crumbs are golden.
When the chicken is almost done, in a medium saucepan, melt the 2 tablespoons butter. Stir in the flour, whisking constantly. Cook the flour/butter mixture for 1-2 minutes. Slowly pour in the milk while whisking quickly. Stir in the chicken bouillon granules and salt. Whisk mixture constantly over medium heat until the mixture begins to simmer and thicken, about 3-5 minutes.
Once the sauce has bubbled and thickened, remove from heat and stir in the mustard, Worcestershire sauce and Parmesan cheese. Stir until the cheese is melted. Keep the sauce warm until the chicken is finished baking. If your sauce is too thick, whisk in some more milk. If it’s too thin, simmer longer.
Serve each chicken cordon bleu portion with warm sauce.