In a food processor or liquidiser, pulse together macadamia nuts and breadcrumbs until finely ground. Pour nut mixture onto a plate and coat fish fillets on both sides.
Heat butter in a large frying pan over medium heat. Fry fillets on both sides until nuts are golden brown. Remove to a baking tray.
Add shallots to frying pan, cook until translucent. Stir in chicken stock. Mix in pineapple, papaya, mango, coconut and chillies. Season with salt, pepper and sugar to taste. Simmer until sauce is thick, about 30 minutes. Pass through a sieve to remove chillies, fruit and shallots. Reserve sauce in a pan over low heat.
Bake mahi mahi in preheated oven about 10 minutes, until internal temperature reaches 60 degrees C. Remove fish and lightly coat with sauce.