Prep all ingredients: clean and slice the squid, devein the shrimp, smash the lemongrass, tear the lime leaves, and slice the galangal.
Bring water to a gentle boil in a medium pot. Add galangal, lemongrass, and kaffir lime leaves. Simmer until fragrant.
Stir in tamarind paste, fish sauce, palm sugar, and salt. Let everything dissolve.
Add mushrooms and cook until just tender.
Add shrimp and squid. Simmer for a few minutes until cooked through.
Lower the heat and add coconut milk. Warm through gently, don’t let it boil.
Turn off heat and top with optional herbs or chilies. Remove the galangal and lemongrass before serving, if preferred.