25g dried porcini
1 red onion, roughly chopped
1 clove garlic, crushed
200g chestnut mushrooms, roughly chopped
1 tbsp flour
3 tbsp sherry
1 dsp tomato paste
½ tsp dried thyme
Soak the porcini in 100mls of hot water for 20 minutes, then drain them over a small bowl reserving the soaking liquor; roughly chop the porcini and set aside.
Melt the butter in a largish pan and sauté the onion for five minutes; add the chestnut mushrooms and garlic and cook for another five minutes. Stir in the flour and cook for a couple of minutes then pour in the stock and the reserved porcini liquor and stir well then add the sherry, tomato paste, thyme and porcini. If the flour goes lumpy, ignore it; you’ll be blitzing it later, anyway. Bring to the boil, stirring; turn the heat down to a simmer, pop a lid on, and let it bubble gently for fifteen minutes. Blitz with a stick blender until smooth, adding a little more stock if necessary to bring it to a consistency you're happy with.
You can freeze this until needed then defrost and reheat thoroughly before serving.