01 -
In a medium bowl, toss shredded chicken with BBQ sauce until well coated. Add red onion and cilantro if using.
02 -
Lay out the bread slices and spread butter on one side of each. On the unbuttered side of four slices, layer 1 slice of cheese, a generous scoop of BBQ chicken, and another slice of cheese. Top with remaining bread, buttered side facing out.
03 -
Heat a skillet or griddle over medium heat. Grill each sandwich 3–4 minutes per side, pressing lightly with a spatula, until bread is golden brown and cheese is melted.
04 -
Slice and serve hot.