In a bowl, toss the shredded chicken with the BBQ sauce. Start with 1/2 cup and add more if you like it saucier.
Season with a pinch of salt, black pepper, and smoked paprika if using.
In a small dish, mix the softened butter and mayonnaise. This blend gives a golden, crispy crust. Spread a thin layer on one side of each bread slice.
Preheat a large skillet or griddle over medium heat.
If your pan tends to stick, add a drizzle of olive oil.
Assemble each sandwich on a cutting board: buttered side down, add a slice of cheddar, a generous layer of BBQ chicken, a few slices of red onion and jalapeño (if using), and a slice of provolone. Top with the second slice of bread, buttered side up.
Transfer sandwiches to the hot skillet. Cook for 3–4 minutes per side, pressing gently with a spatula.
Aim for deeply golden bread and fully melted cheese. Reduce heat to medium-low if browning too quickly.
Once done, move sandwiches to a cutting board. Let rest 1 minute so the cheese sets slightly, then slice in halves or quarters.
Sprinkle with chopped cilantro or parsley if you like.
Serve hot with extra BBQ sauce for dipping and a side of crisp pickles or a simple slaw.