Soak dried chillies in boiling water for 10-15 minutes until soft; then squeeze out excess water and process in a food processor with fresh chilli, onion, garlic, lemongrass, and ginger to a medium coarse paste.
Heat oil in a wok, add the chilli mixture and cook for 10 minutes. Add sugar, tamarind, and water. Cook for 15 minutes until dark and jammy.
Stir in fish sauce, cool slightly, and transfer to a sterilised jar.
Store in the fridge and use within one month.
