To begin, place a large pan over a medium heat and add a dash of oil. Add the onion and sweat until translucent
Finely chop the chestnut and large flat mushrooms then add to the pan with a splash more oil. Sweat down until soft
Boil a kettle and pour 100ml of hot water over the dried mushrooms
After about 5 minutes the dried mushrooms should be soft. Reserve the stock and add the rehydrated mushrooms to the pan
Add the nutmeg, mace and garlic powder to the pan, stir for 30 seconds then add the rest of the ingredients, including the mushroom liquid. Simmer over a low heat for 10 minutes, stirring to avoid any sticking
Transfer to a blender and blitz until smooth
Taste and adjust the seasoning if necessary. To adjust the consistency, return to the pan and reduce to thicken, or add a splash of water and re-season to loosen it
Store in an airtight container in the fridge for up to a month
