Assam Spicy Shrimp

• 4 garlic (cloves)
• 2 onions (red)
• 1 blachan
• 500 gr headless shrimp
• 350 ml water
• 70 gr tamarind
• 55 gr packed brown sugar
• 36 gr young ginger root
• 20 ml oyster sauce
• 16 ml oil