Preheat oven to 400 degrees.

In a sauce pan over medium heat, whisk butter and flour together and cook for 2 minutes.

Then slowly pour the milk into the butter/flour mixture while whisking. Cook until sauce is thickened.

Remove from the heat and whisk in 1/2 cup of the Swiss cheese along with the salt, pepper, nutmeg, and Parmesan cheese. Whisk until the cheese is fully melted and set aside.

Place the halved croissants on 2 baking sheets with the cut sides up. Bake at 400 for 4 minutes.

remove croissants from the oven and turn over so cut sides are down. Place back in the oven for 2 minutes.

remove croissants from the oven and assemble the sandwiches. on the bottom half of the croissant, spread some honey dijon mustard followed by a couple slices of ham and a sprinkle of half of the remaining Swiss cheese.

Continue until all sandwiches are made. Place them on a baking cheese and top evenly with the reserved cheese sauce.and sprinkle with the remaining Swiss cheese.

Bake sandwiches for 5 minutes. Then broil until the top of the sandwiches are golden brown.