Indian-spiced fish cakes

INGREDIENTS

• 600g potatoes , quartered if large
• ½ tsp cumin seeds
• 2 spring onions , finely chopped
• 1 red chilli , deseeded and finely chopped
• 2 tbsp chopped coriander
• 1 egg , beaten
• 100g cooked leftover salmon , flaked into large pieces
• plain flour , for coating
• 25g butter and 1 tbsp sunflower oil
• leftover avocado mayo, raita or mango chutney, to serve