Adam Liaw's barramundi curry with tomato and coconut

Ingredients

• ¼ cup vegetable oil
• 1 tsp fennel seeds
• 1 tsp black peppercorns, crushed
• 4 cardamom pods, bruised
• 1 cinnamon quill
• 10 curry leaves
• 1 onion, peeled and thinly sliced
• 2 garlic cloves, roughly chopped
• 2cm ginger, peeled and roughly chopped
• 2 large green chillies, sliced
• 2 coriander plants, leaves picked, stalks and roots roughly chopped
• 2 tsp ground coriander
• 2 tsp turmeric powder
• 1 tsp chilli powder (or to taste)
• 3 tomatoes, roughly chopped
• 2 tbsp tamarind puree
• 400ml coconut milk
• 1 tbsp fish sauce
• ½ tsp sugar (or to taste)
• 10 okra, trimmed (optional)
• 750g skinless barramundi fillets