In a food processor or blender 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 frypan over medium heat. Fry fillets on both sides until nuts are golden brown. Remove to a baking pan.
Add eschallots to frypan and 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. Strain to remove peppers, fruit and eschallots. Reserve sauce in a pan over low heat.
Bake mahi mahi in preheated oven about 10 minutes. Remove fish and lightly coat with sauce.