Preheat the oven to 200°C/400°F/ Gas Mark 6. Cook the peas in boiling water for 1 minute and drain. Heat half the oil in a frying pan and add the onion and garlic. Cook over a medium heat for 5 minutes until softened and starting to brown.
Add the root vegetables and cook for a further 3 minutes until golden and warmed through.
Stir in the curry powder and cumin and cook for a further minute. Add the peas, coriander and seasoning, then set aside to cool.
Brush a sheet of filo with oil then fold in half. Cut in half across the diagonal to make 2 triangles. Place a large spoonful of the filling on one end of a triangle of pastry and fold over to cover the filling, then keep folding until you have a triangular parcel. Pinch the edges together to seal. Repeat to make 12 samosas in total.
Place on a dampened baking sheet and bake for 15 minutes until crisp and golden. Serve with the yoghurt mixed with the mint sauce.