1. Pickled onion: Slice the red onion into thin slices. In a glass, mix vinegar, water, sugar, and salt. Add the onion, stir, and let it sit for at least 15 minutes.

        2.  Season the chicken breasts and pan-fry them until golden brown. Once cooked, let the meat rest for 5 minutes, then shred it with a fork.

        3.  In the same pan, melt the butter, add the chopped onion, and sauté for 5–7 minutes until soft. Add the shredded chicken, BBQ sauce, and a little water if needed. Cook for 5–8 minutes until the mixture thickens and becomes juicy (it should not be watery).

        4.  Preheat the oven to 190°C (or 180°C fan). Place the bottom halves of the buns in a baking tray. Add a slice of cheddar to each bun, then top with BBQ chicken. Spread the drained pickled onion over the chicken (lightly pat dry if needed), then sprinkle with grated mozzarella. Cover with                   the top halves of the buns.

        5.  Cover the tray with foil and bake for 10 minutes until the cheese melts. Then remove the foil and bake for another 3–5 minutes until the tops are lightly golden.

        6.  After baking, you can brush the tops with garlic butter for extra flavor.