Preheat the oven to 425°F and place a baking sheet on the center rack.
Lightly pound the chicken tenderloins to about 1/4-inch thickness. Season with salt and pepper and set aside.
Heat 1 tablespoon of butter in large pan over medium heat. Add the onions and sauté until soft and pale golden in color, about 3 minutes. Add the fresh thyme leaves, season lightly with salt and pepper and transfer to a small bowl.
Heat the remaining tablespoon of butter in the pan and add the chicken. Cook until no longer pink in the middle, about 1-1/2 to 2 minutes per side and transfer to a plate.
To assemble the sandwiches, spread about 1 ounce of the Ile de France Camembert on each of 4 slices of bread. Top with a portion of apples, then a layer of onions. Drizzle with a small amount of honey, then add 2 pieces of chicken. Top with the remaining slice of bread. Press the sandwiches with the back of a spatula to flatten, then brush the outsides of the sandwiches with melted butter.
Remove the preheated baking sheet from the oven and place the sandwiches on it Camembert side up. Watch carefully and when the top of the sandwich appears golden and toasted, remove from the oven, about 3 to 4 minutes. Carefully flip the sandwiches over and return to the oven until the second side is toasted as well, about 2 minutes.
Transfer to serving plates and allow to rest for about 2 minutes before cutting.
Tips for Making This Recipe
Oven grilling is an easy way to get a few cheese filled sandwiches perfectly browned and done all at the same time, but oven temperatures can vary, so be sure to watch your sandwiches carefully when toasting. Even a few extra seconds can cause them to burn.