Method

1. Heat a large, heavy-based pan with a third of the oil and butter, add the shallots and cook on high heat for 10 minutes, stirring, until soft and brown. Transfer to a bowl.
2. Add another third of the oil and butter to the pan, and cook the chestnut and shiitake mushrooms on medium-high heat for a minute without stirring. Stir, cook for a minute, then add to the bowl. Repeat with the oyster and buna shimeji mushrooms.
3. Tip everything back in the pan, add the stock and lots of salt and pepper, and simmer vigorously for 8 minutes, until reduced by two-thirds. Add the crème fraîche and cook on low heat for 8 minutes. Once a relatively small amount of thick sauce is left, add the ouzo and herbs, adjust the seasoning to taste and set aside to cool.
4. Meanwhile, cut the pastry in two and roll both blocks into 4mm-thick squares. Rest in the fridge for 20 minutes, then cut into circles, one 27cm in diameter, the other 29cm. Leave to rest in the fridge again for at least 10 minutes.
5. Heat the oven to 200C/390F/gas mark 6. Place the smaller circle on a baking sheet lined with greaseproof paper, spread the cold mushroom filling on top, leaving a 2cm border all around. Brush the edge with egg, lay the other circle on top and seal the edges. Use a fork to make decorative parallel lines around the edge. Brush with egg and use the blunt edge of a small knife to create circular lines running from the centre to the edge, just scoring the pastry but not cutting through it.
6. Bake for 35 minutes, until golden on top and cooked underneath. Serve warm or at room temperature.