Heat the oil in a deep frying pan that has a lid or in a large saucepan over a medium heat. Cook the cumin seeds in the oil for a few seconds until they start to crackle, then stir in the ginger and garlic, and cook for a minute more. Mix in the curry powder and cook for another minute. Stir through the potatoes until completely coated in the spice mix and cook for 4 mins.

Pour about 75ml water over the potatoes and season with salt. Put the lid on and cook over a medium-high heat for 12 mins, until the potatoes are just cooked and most of the water has been absorbed. Add the spinach, cover the pan and cook for a minute. Remove the lid and cook for another 5 mins until the spinach is completely wilted and there’s no liquid in the pan. Turn off the heat and season with the garam masala. Leave to cool. Will keep chilled for up to two days.

To assemble the pies, mix the egg with the turmeric and a pinch of salt in a bowl and set aside. Roll the pastry out on a lightly floured surface to the thickness of a pound coin and cut out four circles about 12cm wide, arranging them on a baking tray lined with baking parchment. Put a quarter of the potato mixture into the middle of each pastry circle, leaving a border. Re-roll the pastry offcuts, then cut out four more circles, about 8cm wide. Brush the borders of the larger pastry circles with the spiced egg, then drape the smaller circles over the potato filling. Pinch the borders to seal. Brush the pies with more of the spiced egg and scatter over a pinch of cumin seeds. Will keep frozen for up to two months. Defrost fully before baking.

Heat the oven to 220C/200C fan/gas 7 and bake the pies for 30-35 mins until deep golden. Leave to cool a little, then enjoy warm or leave to cool completely and eat like a pasty with mango chutney or lime pickle. Will keep chilled for two days in an airtight container.