Mushroom & chestnut Wellington

1. Bring a large pan of water to the boil, add the spinach and blanch for 1 minute. Drain, refresh under cold water then squeeze out as much liquid as possible. Roughly chop and set aside.

2. Heat the butter and oil in a large saucepan and gently cook the leeks for 5 minutes until softened and caramelised. Add the thyme and garlic, fry for 1 minute then add the mushrooms and fry for 5-8 minutes more until softened and any liquid has evaporated. Remove from the heat, stir in the chestnuts and leave to cool.

3. Tip the cooled mixture into a large bowl and stir through the goat's cheese and spinach. Lay a large sheet of baking parchment on the work surface and tip the mixture into the middle. Mould into a rough log shape, then roll up tightly in the parchment to make a 26cm-long cylinder. Chill until firm.

4. Preheat the oven to 200°C, gas mark 6 and line a baking sheet with parchment. Dust the work surface with flour and roll the pastry into a 34 x 28cm rectangle. Lay the cylinder of filling on top and unwrap. Whisk together the egg yolk and milk, then brush along the edges of the pastry. Carefully roll the filling in the pastry, finishing with the join on the underside. Press the ends together and trim, then seal and crimp with your fingertips or a fork. Cut any pastry trimmings into festive leaves and use to decorate the Wellington, using a little of the egg wash to stick them on. Place on the prepared baking sheet. Brush with the remaining egg wash, then use a sharp knife to make two holes in the top for the steam to escape. Bake for 30 minutes until the pastry is golden brown and crisp. Leave to stand for 5 minutes before serving, scattered with fresh thyme sprigs, if liked.

COOK'S TIPAny leftovers are great on Boxing Day – try serving with a simple salad.