Preheat the oven to 180 degrees Celsius (350 degrees Fahrenheit)
Toss shredded chicken in BBQ sauce; set aside. (Pro tip: easiest way to get really nice shredded chicken is to pulse a few times in a food processor. Do this in batches. You will end up with an mazing result.)
Start assembling the sandwiches! Lightly brush some BBQ sauce on the bottom side of the sandwich bread then add the following: shredded chicken, mozzarella, red onion slices, and Parmesan. Cover with the top slice of bread.
Using a pastry brush or spoon, brush some melted butter on top of the sandwiches. Bake until cheese has melted.
Once done, remove from oven and serve warm. Something that makes my BBQ sandwiches differ slightly from most is that I add a little bit of white pepper to give it a little kick after its done cooking. Just peel back the top slice of bread and sprinkle some on.
