I would really love to see you guys make this sandwich if you've never had it before. I'll put it to you like this: If you can make a sandwich or a grilled cheese, you will be able to make this sandwich; and you'll thank yourself.
2 slices bread
2 ounces deli ham (french is recommended)
1 1/3 cup grated gruyere cheese, divided
2 tsp whole grain mustard
sliced chives for garnish *optional*
fresh cracked black pepper to taste
3 Tbsp all purpose flour
4 Tbsp unsalted butter
2 cups warmed milk
*optionally you can add a bay leaf to the warm milk before adding it to the bechamel*
scant 1/4 tsp ground nutmeg (fresh grated is ideal)
Heat whole milk over medium heat until it barely reaches a boil. Add a bay leaf.
In a separate pan over medium heat, add the unsalted butter and wait until fully melted. Next add the flour and whisk together until it forms a cohesive paste. Let cook for 1-2 minutes to cook out the remaining starchy floury taste.
Remove the bay leaf from the milk and add it in batches to the roux, whisking in between to make sure everything is incorporated. Once all of the milk is added, let it sit and simmer to allow the flour to fully thicken.
Take your bread, and on the inside of the two slices spread on your whole-grain mustard.
Take your Gruyere and grate a generous amount on the bread. Add your ham on top. Grate the remainder of the cheese on top of the ham. Hit with a little fresh cracked black pepper and compact two slices of bread together.
In a preheated pan, melt 2 tablespoons of butter on medium heat. Add your sandwich and toast for 2-3 minutes per side until brown and crispy. Remove from the pan and place on a sheet tray.
Pour bechamel sauce over the top of the sandwich, enough for it to dribble down the sides. Place sandwich under the broiler for 10 minutes
In a skillet on medium heat, melt your butter and add a whole egg into the pan. Once the outside whites start to cook but the yolk is still runny, flick the hot butter onto the uncooked parts to get them to cook faster.
Remove the sandwich from the oven and place your fried egg on top. Serve with freshly chopped chives and cracked black pepper.