Creamy chicken, mushroom and leek pie. To get started, preheat the oven to 200 degrees Celsius. To make the filling, heat a little oil in a large frying pan over high heat. Cook the chicken in batches, stirring occasionally, for 5 mins or until golden brown. Transfer to a heatproof bowl. Heat a little more oil in the pan. Add leek and cook, stirring, for 2 mins or until the leek softens. Add to the chicken in the bowl. Heat more oil in the pan and add the mushrooms. Stir them and cook for 2 to 3 minutes or until they’re tender. Now return the chicken and leek to the pan. Sprinkle with flour and cook, stirring, for another 2 minutes or until well combined. Stir in the mustard, miso paste and stock and bring to a simmer. Keep stirring for 5 minutes or until the sauce boils and thickens. Then turn off the heat and leave it to cool slightly. Stir in the cream and tarragon and season with salt and pepper. Then spoon the filling into your pie dish. Cut pastry sheets into 3 centimetre strips and lay them over the filling, slightly overlapping them as you go. Trim off the excess pastry with a knife. Brush egg all over the pastry and sprinkle with sesame seeds. Pop in the oven to bake for 25-30 minutes or until the pastry is puffed and golden. This classic creamy chicken pie is easy to make, packed with veggies and full of flavour.