Preheat your oven to 200°C and line a baking sheet with parchment paper.
Whisk the honey and Dijon mustard in a small bowl until well combined.
Place the bacon slices in a single layer on the prepared baking sheet.
Using a pastry brush or spoon, generously brush the honey and Dijon mixture over each slice of bacon, coating them evenly.
Sprinkle freshly ground black pepper over the glazed bacon slices according to your preferences.
Place the baking sheet in the oven and bake for 15-20 minutes until the bacon turns crispy and the glaze caramelises.
Keep a close eye on the bacon while it bakes to prevent it from burning. If desired, you can flip the bacon slices halfway through cooking for even more browning.
Once cooked, remove the baking sheet from the oven and transfer the bacon slices to a plate lined with paper towels to absorb any excess grease.
Set up a grill over medium coals. Take a slice of butter-coated white bread and place two pieces of honey-glazed bacon on top. Add three slices of brie cheese and then the red onion. Top with another slice of white bread to form a sandwich.