Seafood skewers with nam jim

Ingredients

• 16 green prawns, peeled, deveined, tails intact
• 16 scallops, cleaned
• 2 tablespoons oil
• 1 lemongrass stalk, white root finely chopped
• 1 clove garlic, crushed
• 8 soaked bamboo skewers
• Nam jim
• 2 long red chillies, seeded, chopped
• 4 coriander roots, washed
• 1 clove garlic, large, peeled
• 1/4 cup lime juice, (about 1 lime)
• 1 1/2 tablespoon brown sugar
• 1 tablespoon fish sauce