Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper and arrange thick-cut bacon strips in a single layer. Bake for 15-20 minutes or until the bacon is golden and crispy. Once done, transfer the bacon to paper towels to drain excess grease.

In a small bowl, combine equal parts of BBQ sauce and mayonnaise, mixing until smooth. Set aside to allow the flavors to meld.

Butter one side of each slice of sourdough bread generously. Set aside.

Heat a skillet over medium heat. Place a buttered slice of sourdough bread, butter side down, into the skillet. Add a slice of cheddar cheese on top and melt for 2-3 minutes.

Place a generous portion of tender, cooked chicken breast on top of the melted cheese.

Spread BBQ-mayo mixture on the unbuttered side of remaining sourdough slices. Assemble these slices on top of the chicken-covered bread, sauce side down.

Artfully arrange slices of avocado, tomatoes, bacon, and romaine lettuce on top of the chicken layer. Season lightly with salt and pepper.

Place the remaining buttered bread slices on top, butter side up. Gently press down to meld the elements together.

Flip the sandwich in the skillet to toast the buttered side until golden brown, about 2-3 minutes. Repeat on the other side until both sides are toasted.

Remove the sandwich from the skillet, allow to cool slightly, and slice diagonally before serving.