Fry mustard seeds in oil for ten seconds until they splutter.
Sauté onion and ginger for three minutes over high heat.
Stir in peas, spices, mango powder, salt, and a splash of water.
Cook for two minutes then mix in crushed potatoes and fresh coriander.
Preheat the oven to 200°C.
Brush a filo pastry sheet with butter and fold into a long strip.
Place one teaspoon of filling at the end of the strip.
Fold the pastry diagonally into a triangle and repeat to the end.
Brush the outside with butter and sprinkle with sesame seeds.
Bake for 35 minutes until golden, turning halfway through.
Serve warm with chutney on a large plate.