Preheat the oven to 250˚F.
Butter your buns with the softened butter.
Heat a nonstick sauté pan until it is warm, and add the buttered buns.
Reduce the heat the medium or medium-low, and lightly toast the inside of the buns until they are golden-brown, or about five minutes.
*Moving the buns around in the pan as they cook helps to ensure a more even golden-brown color on the final product.
When the buns are toasted, remove them from the sauté pan, and add one slice of cheese to the open side of each piece of bread.
Place the griddled buns with cheese on a parchment-lined sheet tray, with the cheese facing up.
Place the sheet tray with the cheesed buns inside the warm oven to melt and crisp-up at 250˚F while you prepare the remaining sandwich ingredients.
For the chicken, add a light layer of sunflower seed oil to the bottom of the sauté pan, and turn the heat up to medium.
Season your thinly-sliced chicken fillets with Kosher salt, cayenne pepper, and smoked paprika.
Sauté the chicken breasts over medium heat in the same sauté pan that was used to griddle the buns.
While the chicken is cooking, combine the finely-sliced red onions with some lime juice, and set the lime-pickled onions aside in a small bowl.
*You can also use a splash of red wine or sherry vinegar, if you don’t have fresh lime in your kitchen.
Add a few drops of sherry or red wine vinegar and some freshly-ground black pepper to the finely-sliced lettuce, and set the seasoned lettuce aside in a bowl.
When the chicken fillets are done cooking, turn off the heat, and remove the chicken fillets from the skillet.
When the chicken is fully cooked-through and you are ready to assemble the sandwiches, remove the toasted buns with melted cheese from the oven.
Assemble your sandwiches with the toasted buns, seasoned chicken fillets, shredded lettuce, thinly-sliced red onion, finely-sliced tomato, yellow mustard, and a drizzle of honey.