Preheat oven to 180 C and grease a baking tray (I used a 9inch tray).
Place bottoms of the buns in the tray so that they fit together.
Mix the chicken with the BBQ sauce and spread this mix on the buns.
Top with sliced onion rings and then add the cheddar cheese.
Cover with the tops of the buns and bake until the cheese melts.