Preheat Oven and Prepare Croissants:

1. Preheat your oven to 375°F (190°C) and lightly grease a 9×13 inch baking dish.
2. Slice each croissant in half horizontally.
3. Layer the bottom half of each croissant with a half slice of cheese, a slice of ham, and another half slice of cheese.
4. Top with the other half of the croissant to create a sandwich.

Make the Spread:

1. In a small bowl, combine the softened butter, yellow mustard, honey, and Worcestershire sauce. Mix until smooth.

Assemble and Bake:

1. Spread the butter mixture evenly on the inside of each croissant sandwich.
2. Place the assembled croissant sandwiches in the prepared baking dish.
3. Whisk together the egg white with a splash of water in a small bowl.
4. Brush the tops of the croissants with the egg wash and sprinkle with poppy seeds.
5. Bake in the preheated oven for 15-18 minutes, or until the cheese is melted and the tops are golden brown.