Melt dark jaggery in water and strain to remove impurities.
Whisk rice flour, coconut milk, and jaggery syrup together in a heavy pan until smooth and lump-free.
Cook on medium-low heat, stirring constantly with a wooden paddle to prevent sticking.
Gradually drizzle in ghee as the mixture thickens and turns dark and glossy (about 40 minutes).
Stir in cardamom powder, pour into a greased dish, let set completely, and slice to serve.