Lentil and Mushroom Pie with Wholemeal Pastry

Method

1. To make the pastry, tip the flours and a pinch of salt into a bowl, add the butter and rub it into the flour with your fingers until you have a breadcrumb texture. Alternatively, use a food processor to pulse. Add 3–4 tablespoons of ice-cold water and use a knife to stir until it starts to clump, then quickly bring together into a disc with your hands. Wrap and chill in the fridge for at least 25 minutes while you cook the filling.
2. In a shallow casserole or ovenproof frying pan over a moderate heat, cook the onion, leek, celery and carrot in the olive oil for 10 minutes until very soft. Stir in the garlic and thyme and cook for 1 minute until aromatic. Add the mushrooms and cook for 7–8 minutes until all the liquid has been released and then cooked away. Add the flour, tomato purée and miso and cook for 2 minutes, then stir in the stock and keep stirring until it comes to the boil to prevent any lumps. Reduce the heat and simmer for 5 minutes.
3. Remove from the heat and stir in the Worcestershire sauce (if using), the lentils, mustard, cream and tarragon, then season to taste with a little salt if needed (it should be quite well seasoned from the stock and miso) and a generous amount of pepper. Put to one side to cool a little.
4. Preheat the oven to 200°C/180°C fan/400°F/Gas 6.
5. Roll out the pastry to about 3mm (⅛in) thick and the same diameter as the pan (use the lid as a guide if it has one). put the pastry lid on top of the lentil mixture in the pan and pierce the middle with a hole. Crimp the edges with a finger or fork to seal and brush with the beaten egg. Bake for 40 minutes until golden brown. Rest for 5 minutes before serving.