Asian-style snapper broth

Ingredients

• 1 tbsp peanut oil
• 3 cm piece ginger, thinly sliced
• 2 red shallots, thinly sliced
• 2 cloves garlic, thinly sliced
• 1 tsp finely chopped coriander roots
• ½ tsp white peppercorns, crushed
• 500 ml fish stock (2 cups)
• 60 ml light soy sauce (¼ cup)
• 1 tbsp brown sugar
• 150 gm oyster mushrooms, larger ones torn lengthways
• 1 bunch gai lan (Chinese broccoli), trimmed
• 4 snapper fillets (about 200gm each)