Creamy Chicken and Leek Pie

Build the filling. Slowly pour in the chicken stock while stirring until the sauce is smooth and thickened. Stir in the Dijon mustard, heavy cream, thyme sprigs, bay leaves, the remaining 1/2 teaspoon salt, and the remaining 1/4 teaspoon black pepper.

Finish the filling. Return the chicken and any collected juices to the pan. Bring to a gentle simmer and cook for about 5 minutes, stirring regularly, until the sauce is thick and creamy. Remove from the heat and let the filling cool completely, about 1 hour.

Assemble the pie. Heat the oven to 200°C/375°F, or 180°C fan. Spoon the cooled filling into a 1.5 litre baking dish. If needed, join the puff pastry sheets with a little egg white, then cut a lid large enough to cover the dish. Lay the pastry over the filling and press the edges to seal. Cut a small vent in the center.

Bake and serve. Brush the pastry with beaten egg yolk and bake for 45 minutes, or until the top is deeply golden and puffed. Let the pie rest for 5 minutes before serving.