Cook the Chicken:
Heat a skillet or grill pan over medium heat. Season the chicken breasts with salt and pepper on both sides.
Cook the chicken for 5-6 minutes per side, or until the chicken reaches an internal temperature of 165°F (74°C) and is cooked through.
Remove from the pan and let it rest for a few minutes before slicing into thin strips.
Cook the Bacon:
In a separate skillet, cook the bacon over medium heat until crispy, about 4-5 minutes. Drain on paper towels to remove excess grease.
Make the Creamy Sauce:
In a small mixing bowl, combine the mayonnaise, Dijon mustard, lemon juice, garlic powder, salt, and pepper. Stir until smooth.
Toast the Bread:
Toast the slices of bread in a toaster or on a dry skillet until golden and crispy.
Assemble the Sandwich:
Spread a generous amount of the creamy sauce on each slice of toasted bread.
On one slice, layer the cooked chicken, bacon, sliced avocado, lettuce, and tomato.
Top with the second slice of bread, sauce side down.
Serve:
Cut the sandwich in half, and serve immediately with your favorite side (chips, salad, or fries).