I’ve always loved serving individual pies. It instantly elevates a casual family dish into something a bit smarter, but without really increasing the work. The twist here is that the lids are cooked separately from the pie filling. If serving more than two or three people, simply double the quantities for the filling, but the amount of pastry required depends on the size of your dish(es). Use the meat from the chicken thigh and leg as it is less likely to dry out than the breast.
Fry the pancetta in a hot, dry pan for 3–4 minutes until lightly golden. Tip onto a plate lined with paper towels. Wipe out the pan.
Heat the oil in the pan and sauté the vegetables with the thyme and some salt and pepper for about 7 minutes until softened. Pour in the sherry and bubble for 5 minutes until well reduced. Return the pancetta to the pan and pour in the stock.
Return the liquid to a boil and cook for 10–15 minutes until reduced by half. Stir in the crème fraîche and cook for about 5 minutes until the sauce has reduced by about a third. Check for seasoning, then remove from the heat and set aside.
Preheat the oven to 400°F. Roll out the pastry on a lightly floured surface to ⅛-inch thickness. Cut out 2 or 3 rounds, using a small saucer as a template. Carefully place the pastry rounds on a large, nonstick baking sheet and score the surface in a diamond pattern, using the tip of a small sharp knife.
Brush the pastry with the egg yolk glaze and bake for about 10 minutes until risen and golden. Bake for an additional 2 minutes with the oven door slightly ajar, to help crisp the pastry. Remove from the oven and slide onto a wire rack.
Meanwhile, add the chicken to the sauce and reheat until the meat is warmed through. Check the seasoning and divide the chicken mixture between your warmed serving plates. Top each pile with a pastry round and serve.