Oysters with Ginger and Lime

Name: Oysters with Ginger and Lime
Ingredients: 1 spring onion (scallion), very thinly sliced; 1 small chilli, thinly sliced (optional); 2 teaspoons Thai fish sauce; 2 teaspoons caster (superfine) sugar; 1 tablespoon chopped coriander (cilantro); finely grated zest and juice of 2 limes; ½ teaspoon finely grated ginger