Work 5 tsp spice, 3 garlic cloves, 1.2cm ginger and 1/8 cup water into a loose paste in a mortar and pestle. Fry 1 small chopped onion in oil until golden, add paste and fry until fragrant and bubbling, add 1/2 cup tinned tomatoes and simmer a further 5 minutes after liquid dissolves. Stir in 150ml coconut milk and 1/3 cup of water and simmer a further 5 min. Add fish and vegetables and cook until tender.
India