If using fresh cockles, rinse them thoroughly in a colander and boil until the shells open; remove the meat and discard the shells. Frozen cockles can be used directly after thawing.

Dry-toast the coriander seeds in a pan until fragrant, then let them cool slightly.

Blend the garlic cloves, shallots, fresh ginger, galangal, fresh turmeric, 4 lemongrass stalks, candlenuts, toasted coriander seeds, cumin seeds, and bird's eye chilies into a smooth spice paste.

Heat the cooking oil in a wide pot over medium heat. Add the bruised lemongrass stalk and fry it until aromatic.

Add the blended spice paste to the pot and sauté over medium-low heat until fragrant and the oil begins to separate.

Stir in the chili paste and cook it with the spice paste until the mixture is deep red and oil separates again.

Add the dried tamarind slices and coconut milk. Bring the sauce to a gentle simmer.

Add the toasted grated coconut and simmer, stirring regularly, until the coconut sauce thickens and releases oil.

Add the cockles and simmer gently only until heated through and coated in the thick rendang sauce.

Season the rendang with salt and palm sugar. Stir until the seasonings dissolve.

Stir in the finely sliced turmeric leaves and cook for 1 to 2 minutes. Serve the cockle rendang hot with steamed rice, ketupat, or yellow glutinous rice.