Heat the oil in a small frying pan. Cook the onion in the oil until soft, about 5 mins, then stir in the curry powder and cook for 1 min more. Scrape into a mixing bowl and stir in the mango chutney, followed by the chicken and soured cream, then season.
Heat oven to 200C/180C fan/gas 6. Cut 24 strips of baking parchment as wide as the base of your muffin tin and grease one side with a little butter to help them stay in place. Criss-cross 2 into each hole of a 12-hole muffin tin so the edges of the strips stick out - this will help you remove the pies easily once cooked. Thinly roll out three-quarters of the pastry on a lightly floured surface. Stamp out 12 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 remaining pastry and cut 12 lids. Top each pie with a pastry lid, press together the edges to seal and roll down any excess pastry to make a lipped-edge. Brush the tops with more beaten egg and scatter with almonds. Poke a fork in each to let the steam out while they cook and bake for 20-25 mins or until golden and cooked through.