In a non-reactive bowl place mushrooms in layers and sprinkle with salt.
Cover mixture with cling wrap, and leave in a cool place for 24 hrs.
Stir mixture and press it down with wooden spoon as it macerates.
Put the dried porcini into a small bowl and pour about 250 ml bowling water over them let them soak for an hour.
Scoop porcini out with slotted spoon.
Line sieve with muslin and strain liquid through it into a pan.
Put sliced mushrooms and their liquid into pan.
Add Porcini, and rest of ingredients including spice bag.
Bring to a boil, reduce heat and simmer for 1 1/2 hours, stirring until mixture becomes very thick.
Remove spice bag, blend mushroom mixture in bender until very smooth, in batches if necessary.
Return to boil and simmer 5 minutes.
Pour into sterilized bottles and seal