Croque-Monsieur dipping sauce in a frying pan

Ingredients:

• 1 package (220 g) of rolled out croissant dough
• 5 tablespoons unsalted butter
• 1 medium onion, diced
• 1 clove garlic, minced
• 3 tbsp. flour
• 2 cups of hot milk
• 0.5 tbsp. freshly grated parmesan
• 1 tbsp Dijon mustard
• 1 teaspoon coarse salt
• 0.5 tsp freshly ground black pepper
• A pinch of nutmeg
• 2 cups grated Gruyere
• 4 slices of ham, 30 g each, tear into 5 cm pieces.
• 2 sprigs thyme, leaves removed

Preparation:

1. Preheat oven to 190°C. Separate the dough triangles and form them into croissants, rolling from the wider end of the triangle. Set aside.
2. In a 25cm skillet, melt the butter over medium heat. Transfer 1 tablespoon of the butter to a small bowl; set aside.
3. Add the onion and garlic to the skillet; cook, stirring, until softened and just beginning to brown, about 4 minutes. Reduce heat to low. Add the flour and stir with a wooden spoon to evenly distribute, about 2 minutes. Slowly pour in the hot milk in a steady stream, whisking constantly. Increase heat to medium and cook, stirring constantly, until the sauce thickens, about 5 minutes.
4. Remove from heat, add Parmesan, mustard, salt, black pepper, nutmeg, and 1 teaspoon of Gruyere. Arrange the dough rolls around the outside of the pan, pressing gently to seal each roll to the bottom. Brush the tops of the rolls with the reserved 1 tablespoon of butter. Sprinkle with the remaining 1 cup of Gruyere, spreading it evenly over the cheese sauce and dough.
5. Fold a piece of ham into a small bundle and place it in the cheese sauce, level with the sauce's surface. Repeat with the remaining pieces of ham, distributing them evenly over the sauce.
6. Bake until the bagels are golden brown and the sauce is melted and browned in spots, 15 to 17 minutes. Sprinkle with thyme leaves.