1 Quickly knead together the flour, butter, salt and 2-3 tbsp cold water to form a smooth dough. Wrap in clingfilm and chill for approx. 30 minutes.
2 Heat the oven to 180°C (160°C in a fan oven), 350°F, gas 4 and grease a baking dish.
3 Roll out the dough on a floured work surface and line the baking dish with it. Chill again.
4 To make the topping fry the mushrooms in hot oil until brown and season with salt and ground black pepper. Fry the onions and garlic and stir into the mushrooms. Leave to cool.
5 Mix together the cream, milk, creme fraiche, eggs and half the cheese. Season with salt, ground black pepper and nutmeg. Sprinkle the remaining cheese on the dough in the dish, add the mushroom mixture and the pour the cream mixture on top. Bake for 50-60 minutes until golden brown. If the topping gets too brown cover with tin foil. Serve sprinkled with parsley.