Mushroom and chestnut filo pie

Method

1. Melt 40g of the butter in large, deep frying pan over a medium heat. Add the leeks and garlic and cook for 3-4 minutes, stirring occasionally, until beginning to soften. Add the mushrooms, increase the heat to high and stir-fry for 2-3 minutes, until wilted slightly.
2. Add the wine to the pan and bubble until nearly all of it has evaporated. Reduce the heat to medium-low and stir in the chestnuts, cream, lemon juice and half the thyme leaves. Simmer gently for a few minutes, until the sauce has reduced a little, then season to taste. Transfer to a deep, 1.5-litre freezerproof and ovenproof dish and cool completely.
3. Stir the remaining thyme into the remaining melted butter. Brush half the filo pastry sheets with some of the thyme butter, lay 1 unbuttered filo sheet on top of 1 buttered filo sheet, then brush again with thyme butter. Halve each filo pile through the middle, so you have 8 smaller squares. Scrunch each square, then lay side by side on top of the filling, to give a ruffled filo topping. At this point, freeze or continue cooking to eat immediately. Serve with steamed spring greens.