Pat the thick-cut applewood smoked bacon strips dry with paper towels. In a medium skillet over medium heat, cook the bacon for about 4-5 minutes on each side until it turns a deep amber color and becomes crispy. Transfer the bacon to a paper-lined plate but leave the bacon fat in the skillet.

Reduce the skillet heat to low and add the thin apple slices to the remaining bacon fat. Sauté the apples for about 2-3 minutes until they soften slightly, then stir in the pure maple syrup and whole-grain mustard. Allow the mixture to simmer for another 2 minutes until it thickens, and season with freshly ground black pepper, sea salt, and chopped thyme leaves.

Gather your thick-cut sourdough bread and spread softened unsalted butter generously on one side of each slice. Lay down a slice of bread, followed by a layer of shredded sharp cheddar cheese, the crispy bacon, and the caramelized apple mixture. Top with another slice of buttered bread, ensuring the buttery side faces outward.

Place the assembled sandwich in the same skillet over medium heat, cooking for about 3-4 minutes per side until the bread is golden brown and the cheese is melted. Once both sides are perfectly crisp, remove the sandwich from the skillet.

Let the sandwich sit for a minute before slicing it in half. Drizzle a little maple syrup over the top if desired. Serve immediately.