Preheat the oven to 350 degrees F. Lightly spray a 9 x 13 baking dish with non-stick cooking spray.
Lay 24 of the Ritz crackers in the baking dish.
Top the crackers with pieces of the Swiss cheese and then pieces of the ham.
Top with the remaining crackers.
Whisk together the melted butter, onion powder, poppy seeds, Worcestershire sauce, and Dijon mustard.
Spread the butter mixture over each cracker evenly.
Bake for 5-7 minutes or until the cheese melts.
Serve the crackers and enjoy.
