Peel and devein the prawns. Reserve the heads and shells. Rinse the prawns and set aside.
Place the prawn heads and shells in a pot. Add the boiling water and simmer for 15 minutes. This will be the stock for the dish. Strain the stock and discard the heads and shells (see Note).
Place all the ingredients for the spice paste in a blender and process into a coarse paste.
Transfer the spice paste to a medium saucepan. Add the stock, coconut milk, lemongrass, turmeric powder and asam gelugor. Bring to a boil while stirring continuously to prevent the coconut milk from curdling.
Add the pineapple and turmeric leaf. Season with salt.
Add the prawns and stir gently. Turn down the heat and let it simmer for 2 minutes until the prawns are done. Remove from heat.