Heat the oil in a small frying pan. Cook the onion in the oil until soft, about 5 minutes, then stir in the curry powder and cook for 1 minute more.
Scrape into a mixing bowl and stir in the mango chutney, followed by the chicken and soured cream, then season. Allow to cool.
Preheat the oven to 200°C, fan 180°C, gas mark 6. Grease 8 holes of a muffin tin with the butter.
Unroll the pastry and stamp out 8 circles big enough to line the holes generously, with a little pastry overhang at the top for sealing.
Divide the chicken filling between the pies. Roll out the remaining pastry and cut 8 lids.
Top each pie with a pastry lid, press the edges together to seal and roll down any excess pastry to make a lipped-edge. Brush the tops with the beaten egg.
Poke a fork in the top of each to let the steam out while they cook and bake for 20-25 minutes or until golden and cooked through.
*All information included in this recipe has been provided by BakeAway.