Preheat your oven to 350°F and prepare a 9x13-inch baking dish.
Lay half of the Ritz crackers, flat side down, evenly across the dish.
Arrange the ham strips on top of each cracker, folding them neatly.
Place a piece of Swiss cheese on each layer of ham, then top with another cracker to create sandwiches.
Combine the melted butter with Dijon mustard, Worcestershire sauce, and garlic powder in a small bowl. Drizzle this mixture evenly over the sandwiches.
Evenly sprinkle the poppy seeds and minced onion across the top of the sandwiches.
Bake the dish for 10-12 minutes, or until the cheese has melted and the cracker tops are golden brown.
Serve these warm, flavorful snacks immediately and savor every bite.