Step 1

Preheat oven to 200C. Heat oil in a large non-stick frying pan over high heat. Add the chicken and cook, turning occasionally, for 5 minutes or until brown. Transfer to a plate. Add the mushroom, leek and garlic to the pan; cook, stirring, for 5 minutes or until leek softens. Add the chicken and flour and stir to combine. Add the mustard, stock and sour cream. Reduce heat to medium and stir until sauce thickens. Stir in peppercorns, lemon juice and tarragon. Season with salt and pepper. Set aside to cool.

Step 2

Line four 1 1/2 cup (375ml) capacity pie dishes with shortcrust pastry. Line with baking paper and fill with baking beans. Place on a baking tray and bake for 15 minutes or until lightly golden. Remove paper and baking beans.

Step 3

Spoon chicken mixture evenly among pastry cases. Lightly brush edges with a little egg. Use a 12cm round pastry cutter to cut four discs from puff pastry. Place pastry discs over chicken mixture to enclose. Lightly brush with egg mixture. Use a small sharp knife to lightly score the top of pastry in a diamond pattern. Bake for 20-25 minutes or until pastry is puffed and golden and filling is heated through. Serve immediately.