Heat the oil in a medium pan, add the onion and sauté for 5 mins or until pale golden. Cut the potatoes into small cubes about 1cm square. Add the potatoes to the pan with the curry paste and 150ml water. Bring to the boil and simmer for 10mins or until the potatoes are tender. Stir in the peas cover and simmer for a further 5mins or until the liquid has been absorbed. Remove from the heat, stir in the coriander and season to taste with salt and pepper. Spread out on a plate and leave to cool.
Preheat the oven to 180°C/Fan 160°C/Gas Mark 4. Work with one sheet of pastry at a time, keep the other covered with cling film and a damp tea towel. Brush the pastry lightly with olive oil on one side and cut into 3 long strips. Set a tablespoon of filling at the top of one strip of pastry, oil side down. Fold the corner of the pastry over the filling so that the top edge of the pastry is now over the right edge. Take the point of the strip and fold this down towards the bottom of the pastry to create triangle shapes. Continue folding in this way and brush with any remaining oil to make 12 samosas. Bake for about 20 minutes until crisp and golden.
These crispy triangles of curried vegetables taste great served with pomegranate and mint raita - mix a 250g pot Greek style yogurt with 3 tbsp chopped fresh mint, 100g pomegranate seeds. Season to taste with salt and pepper before serving.