Boil potatoes in salted water for 15 minutes until tender, drain, and mash until smooth.
Stir in butter, cream, curry powder, coriander, chilli, onion, and seasoning then leave to cool.
Discard shell fragments from crabmeat, mix into potatoes, and shape into four round patties.
Fry patties in hot oil for 3-4 minutes per side until golden-brown and drain on kitchen towels.
Melt caster sugar in a pan over medium heat until it forms a light brown caramel.
Blend the remaining chilli sauce ingredients together in a food processor to a smooth purée.
Pour the purée into the rich caramel and stir well.
Bring sauce to a boil, simmer for 5 minutes, then remove from heat to cool.
Serve crabcakes on a plate with the chilli sauce on the side.