Step 1

Process the lemongrass, ginger, chilli, garlic, coriander root and vinegar in a blender, or in a jug using a stick blender, until a thin paste forms. Transfer the mixture to a bowl, then add the fish sauce, lemon juice and caster sugar. Whisk until the sugar has dissolved and the dressing is well combined. Refrigerate until required.

Step 2

When ready to serve, place the oysters on serving plates - on a bed of rock salt if desired to keep Oysters stable. Drizzle each with 2 teaspoons of the dressing, garnish with spring onion and serve immediately.