1. Preheat a fan forced oven to 200°C and grease a 12 hole muffin tin.
  2. Turn the electric frypan to a medium setting and gently melt the butter and oil. Add the leek, garlic and mushrooms and sauté until softened and browned.
  3. Add the chicken and cook for approximately 3 minutes on each side. Pour over the stock and thyme and allow to simmer for 5 minutes.
  4. Combine the corn flour and water and then add to the frypan and sauté for 2 minutes. Turn the frypan off and transfer the mixture to a bowl to slightly cool.
  5. Using a 15cm glass as a cookie cutter, carefully place the glass onto the short crust pastry sheet, making sure to get the most out of the pastry, and cut around the edge of the glass until a perfect circle is formed. Push into the greased muffin pan and repeat until all wells have pastry in them. Do the same with the puff pastry, except with a 12cm glass.
  6. Fill the puff pastry layer with 1 1/2 tablespoon of mixture and then top with the puff pastry round. Gently press each pie rim with a fork and brush with milk, using a pastry brush.
  7. Place into the oven to bake for approximately 20 minutes or until golden brown. Remove and allow to cool on cake racks.