Place rice and split peas in a dry frypan and cook, stirring and tossing frequently, for 7 - 10 minutes until the rice has turned a light golden colour. Cool slightly, place in a blender or mortar and pestle and grind to a powder. Set aside.
Heat oil in frypan. Brown chicken pieces in batches and place in a slow cooker or large ovenproof dish with lid.
Discard all of the oil except 1 tablespoon. Add the onion to the frypan and cook until transparent.
Add the garlic, ginger, curry powder and mustard seeds. Cook stirring for 1 - 2 minutes, until the flavour is released.
Add the tomato puree, coconut milk and rice and split pea powder. Stir until combined.
Pour over chicken and stir through to coat all chicken pieces.
Cook in the slow cook on 'fast' setting for 3 hours or in the oven at 175 degrees celsius for two hours.
Season to taste and serve topped with toasted shredded coconut.