Preheat oven to 350 degrees F. Coat the inside of a 9-inch x 13-inch baking dish with non-stick cooking spray.
Bring a large pot of salted water to a boil. Cook egg noodles according to the package directions.
While the noodles cook, add 2 tablespoons of butter to a medium saucepan. Once melted, whisk in the flour and cook for 1 minute.
Slowly pour in the chicken broth while whisking constantly. Add the milk and simmer until the sauce starts to thicken, whisking often.
Add the Dijon mustard, Worchestershire sauce, thyme, salt, and pepper to the pot. Stir to combine and cook for 3 minutes.
Remove sauce from the heat and add 1/2 cup of Swiss cheese to the sauce. Stir until the cheese it melted.
Place the cooked egg noodles, cooked chicken, and ham in a large mixing bowl. Pour the cheese sauce over everything and stir until well coated.
Pour the mixture into your prepared baking dish and spread it into an even layer. Sprinkle the remaining 1/2 cup of Swiss cheese over the casserole.
Melt 4 tablespoons of butter in a medium bowl. Add the Ritz cracker crumbs and stir that together. Sprinkle the cracker crumbs all over the top of the casserole.
Bake for 20 minutes until the top is golden brown and the casserole is bubbling.
Remove from the oven and sprinkle with chopped parsley and a little shredded Parmesan cheese for garnish. Serve warm.
Notes
I highly recommend shredded your own cheese using a cheese grater or food processor. It melts better and makes the sauce creamier!