Blend all spice paste ingredients with ⅓ cup (80ml) water until smooth.
Place asam jawa in a small metal strainer over a bowl. Pour 1 cup (240ml) hot water over asam jawa. Stir and press down asam jawa with a spoon to dissolve.
In a medium sized pot, heat vegetable oil. Add ground spice paste and kaffir lime leaves. Stir fry for 8 to 10 minutes until fragrant.
Pour strained tamarind juice into the pot. Stir to combine. Place lid on the pot and allow sauce to come to a boil. Reduce heat and continue to simmer for 3 to 5 minutes.
Remove the lid. Add shrimps (prawns), sugar, and salt. Stir to get all ingredients well mixed.
Place lid back onto the pot and continue to simmer for 3 minutes.
Turn off stove. Dish into a serving bowl.
Notes
**You can also use 2 tsp tamarind concentrate mix with 1 cup (240ml) water.