Kale, chestnut and mushroom pie

Method

1. Preheat the oven to 200°C/fan180°C/gas 6. Melt the butter in a large pan over a medium heat. Add the onion, celery and garlic, season, then cover with a lid and cook gently for 10-15 minutes until softened.
2. Drain the porcini (see tips), then roughly chop. Add all the mushrooms to the softened onion mixture with the sage and chestnuts and fry for 5 minutes. Stir in the flour and cook for 2 minutes. Add the milk, little by little, stirring, until the mixture thickens. Season, then leave to cool.
3. Half-fill a large pan with water and bring to the boil. Add the kale and simmer for 3 minutes or until vibrant and tender. Drain and refresh under cold water, then squeeze out the liquid and pat dry in a clean tea towel. Add to the mushroom mix, check the seasoning, then pour everything into a 1.5 litre ovenproof dish.
4. Roll out the pastry on a lightly floured surface to the thickness of a £1 coin. Trim so it’s a little bigger than the dish (see tips). Brush the rim of the dish with a little beaten egg. Cut the pastry trimmings into strips, lay over the rim, then brush with a little more egg. Lay the rolled-out pastry over the top and press the edges to seal. Cut shapes from any leftover pastry to decorate (see tips). Brush the pie generously with the remaining beaten egg, then bake for 25 minutes until crisp and golden.