Marinate chicken with chilli sauce, chilli garlic sauce, soya sauce, salt and pepper for 10 minutes.
Sprinkle flour and mix well.
Heat oil and fry chicken till light golden.
Now cut the bun into ½ length wise, and toast slightly with 1 tbsp oil in a pan, keep aside.
Saute 2 onions (cut into rings) in 2 tbsp oil for 2 minutes, spread mustard paste on each piece of bun.
Then mix fried chicken with capsicum and ketchup, spread chilli chicken topped with onion rings.
Cover with half bun, cut into half, fix with toothpicks, roll in butter paper and serve hot.