Preheat the oven to 400F/200C and spread 2 tablespoons of BBQ sauce on one side of the naan bread.
Toss the sliced onion in the olive oil and cook in the microwave for 1 minute, until soft. Scatter the onion and chicken breast over the naan bread.
Sprinkle over the shredded mozzarella cheese and bake at the top of the preheated oven for 10 minutes, or until the cheese starts to melt and the naan bread is crisp.
Optional: drizzle over an extra 1 tablespoon of BBQ sauce before slicing and serving.