Preheat your oven to 375°F.
Slice each croissant in half horizontally.
Spread 1 tablespoon of Dijon mustard on the inside of each croissant half.
Layer the sliced ham evenly on the bottom half of each croissant, followed by the Swiss cheese.
Place the top half of the croissant back on.
In a small bowl, mix the melted butter, garlic powder, dried parsley, salt, and pepper. Brush this mixture over the top of each croissant.
Place the croissants on a baking sheet lined with parchment paper.
Bake in the preheated oven for 12-15 minutes, or until the croissants are golden brown and the cheese is melted.
Remove from the oven and let cool for a couple of minutes before serving.