01 - Preheat a large skillet or griddle over medium heat.
02 - In a separate pan, cook the beef bacon over medium heat until crisp, approximately 3 to 4 minutes per side. Drain the cooked bacon on paper towels.
03 - Liberally butter one side of each bread slice.
04 - Place 4 bread slices, buttered side down, on a clean work surface. Layer each slice with 2 slices of cheese, followed by 2 slices of crispy beef bacon. Optionally, add thinly sliced tomato or red onion. If desired, spread a thin layer of Dijon mustard.
05 - Top each assembled sandwich with the remaining bread slices, ensuring the buttered side faces upwards.
06 - Carefully place the assembled sandwiches into the preheated skillet. Grill until each side is golden brown and the cheese is thoroughly melted, requiring about 3 to 4 minutes per side. Gently press down on the sandwiches with a spatula to promote even browning and melting.
07 - Remove the grilled sandwiches from the skillet. Slice each sandwich in half and serve warm for optimal enjoyment.