Bombay potato & spinach pies

INGREDIENTS

• 1¼kg large waxy potatoes such as Charlotte, halved
• 85g butter
• 2 onions , chopped
• 1 tbsp cumin seeds
• 1 tbsp black mustard seeds
• 2 tbsp finely chopped ginger
• 2 red chillies , halved, deseeded and sliced
• 3 tbsp Korma paste
• 400g bag fresh spinach
• 4 tomatoes , chopped
• small bunch coriander , chopped
• 270g pack filo pastry (6 large sheets)
• 50g melted butter
• 1 tsp black mustard seeds