1Preheat oven to 170°C.
2Place a pie dish (or baking tray) over a medium heat, add a splash of olive oil and butter and sauté onion, carrot and tomato till soft.
3Add some extra butter, chicken and flour, cook until brown. Then, add mushrooms.
4Add Dijon mustard, crème fraiche and chicken stock and stir well.
5Add thyme, rosemary, nutmeg and then season with salt and pepper. Allow to simmer.
6Take off the heat, sprinkle with tasty cheese, salt and pepper and cover pie dish with puff pastry.
7Squeeze with your finger tips to tuck the puff pastry around the edge, brush with egg wash then bake for 15 minutes, or until golden and puffy.
8Remove from the oven and serve.