In a bowl, mash the avocado with a fork. Add the lime juice, sour cream, garlic powder, cumin powder, sea salt, and black pepper and mix well. Set aside.
Season the chicken slices with sea salt and black pepper on both sides. In a skillet, heat 1 tablespoon of the butter over medium heat.
Add the chicken slices to the pan and cook for 2 to 3 minutes per side, until golden and cooked through. Set aside. Do not clean the pan.
Add the remaining tablespoon of butter to the skillet and melt the butter over medium-low heat.
Add the buns, cut side down and toast until golden.
Place a piece of lettuce on top of the bottom half of each toasted bun.
Add a cooked chicken slice, 1 cheddar slice, ½ tablespoon of BBQ sauce, ½ slice cooked bacon, a spoonful of the avocado mixture, and tomato slices on each sandwich.
Top with the bun caps.