Easy potato and pea samosas

INGREDIENTS

• 3 tbsp vegetable oil
• ½ tsp mustard seeds
• 60g/2½oz chopped onion
• 1 tsp finely chopped ginger
• 60g/2½oz frozen peas
• 1 tbsp ground coriander
• 1 tsp ground cumin
• ¼ tsp red chilli powder
• ½-¾ tsp garam masala
• 1-2 tsp dried mango
• , to taste salt
• splash water
• 600g/1lb 5oz potatoes, peeled, boiled until soft and crushed into large lumps
• 4 tbsp chopped fresh coriander
• packet ready-made filo pastry
• 5 tbsp melted butter
• 2 tbsp sesame seeds