Mushroom filo pie

Add the mushrooms and season with salt and pepper. Cover and cook over moderate heat, stirring a few times, until the mushrooms release their liquid, about 8 minutes. Uncover and cook, stirring occasionally, until the liquid has evaporated and the mushrooms are browned, about 8 minutes longer.

In a large frypan, melt another 30g of the butter. Set the final 30g of butter aside. Add the chopped onion and cook over moderate heat, stirring occasionally, until softened, about 7 minutes. Stir in the flour until incorporated, then gradually stir in the chicken stock until smooth. Bring to a boil over moderately high heat and cook, stirring often, until thickened, about 2 minutes. Stir in the mushrooms, thyme and lemon zest. Remove from the heat and season with salt and pepper. Let cool completely.

Melt the remaining 30g of butter and have ready in a little dish with a pastry brush. Line a large rimmed oven tray with baking paper. Place 1 filo sheet on the baking paper and brush lightly with some of the melted butter. Top with the remaining filo sheets, buttering each sheet as you go; reserve about one tablespoon of the butter. Spoon the cooled mushroom filling onto a long side of the phyllo and carefully roll it up like a log, folding in the ends as you go. Shift the strudel to the centre of the baking sheet, seam side down. Brush all over with the reserved melted butter. Bake for about 45 minutes, until your mushroom strudel is golden brown and crisp. Let rest for about 10 minutes, then slice and serve with a green salad.