Puffy flatbread: Add all the puffy flatbread ingredients to a large bowl.
Mix everything thoroughly with a spoon until there's no dry flour in the bowl. This dough should be pretty wet and shaggy.
You will want to knead with your hands at this point, but you should add as little extra flour as possible. I suggest oiling your fingers and possibly adding a little extra oil to the bottom of the bowl before kneading, which should help a little with the sticking problems. Knead as much as you can, about 2 or 3 minutes.
Work the dough into roughly a ball shape and let it rest in the bowl (covered) in a warm spot in your kitchen for one hour.
After one hour, flour a flat surface and dump out your proofed dough. At this point, you will want to divide the dough into 4 or 5 pieces. If you have a scale, I shot for 115 to 125 grams each for an 8 to 10-inch round pastry.
Roll each portioned dough piece out into balls.
Place a large skillet or griddle over medium-low heat.
While the pan is pre-heating, start shaping each dough ball one at a time into a disk. You will need to sprinkle flour on the dough and the flat counter if the dough is really sticky. Press or roll (with a rolling pin) the dough into flatter and wider disks. Flatbread will puff up, but it will not puff out, so the diameter of the disk you have pre-cook is what you will end up with after cooking.
Once you have an 8 to 10-inch diameter disk, transfer it carefully to the hot skillet or griddle. Cook for 2 minutes on the first side and flip. Continue cooking for around 2 minutes on each side until you start seeing brown spots on the dough. The flatbread may puff up during this process and that is a good thing. Press it down with a spatula to keep it consistently cooking.
Once your flatbread is spotted on the outside and puffy, add it to a plate or pan covered with a clean towel. The towel allows the flatbreads to steam themselves a little which makes them even more pliable.
Continue this process for all your dough balls until they are all turned into flatbreads.
Breadstick seasoning: add all the breadstick seasoning ingredients into a small bowl. Stir well to combine. Store in a sealed container or zip-top bag in the refrigerator. This mixture will clump up, but you can shake or stir it well to break up the clumps.
Melt assembly: add your 8 to 10-inch flatbread to a dry skillet over medium heat. After a couple of minutes on the hot pan, the flatbread should be warm and more pliable.
Flip the flatbread over and immediately start adding half of your cheese over one-half of the exposed flatbread. Remember, we're going to be folding this over on itself very soon.
Scatter the small pieces of chicken evenly on top of the cheese and then drizzle on 1 to 2 tablespoons of barbecue sauce. Then scatter sliced red onion and chopped cilantro on top of the barbecue sauce. Top everything with the rest of the cheese and fold the flatbread in half, covering the cheese, meat, and sauce.
Slide the folded flatbread to the side of the pan and add 1 to 2 tablespoons of butter (or oil) directly to the pan. Allow the butter to heat up for 30 to 45 seconds or until it's melty and bubbly and then slide the folded flatbread on top of the bubbly butter. The butter will help fry and crisp up the outside of the flatbread melt. Cook for another 1 to 2 minutes.
After a couple of minutes, flip the flatbread and check to make sure it's turning golden brown. Let the second side cook for another 1 to 2 minutes and flip again. Keep cooking and flipping until both sides of your melt are golden brown and crispy.
Remove the BBQ chicken melt to a cooling rack or a paper towel-lined plate and sprinkle the top with breadstick seasoning.
Allow the melt to cool for 2 minutes and serve.