Put about 3/4 cup dried porcini mushrooms in a small pot, and cover
with 2 cups boiling vegetable stock. Wait one hour. Strain off the
mushroom/stock (there might be a little sand in the dehydrated
mushrooms), reserving mushrooms.
In a pan, dry saute a handful of crushed hazelnuts until lightly
toasted and fragrant.
Add 4 Tbsp butter and 4 tbsp flour, stirring constantly, until it
becomes a darkened roux, 8-10 minutes.
Add a handful of thinly sliced onion and cook until it softens.
(Add a little more butter if necessary to prevent burning.)
Add the mushroom water and two cups of chicken stock (or two more
cups veggie stock), to the roux/onion mix. Add 1/4 cup robust red
wine, or 3 tbsp dry sherry. Add a handful of the rehydrated mushrooms,
finely chopped. Simmer awhile, and add some salt and pepper.
Puree the solids, and pour the entire mix thru a strainer.
Simmer and reduce by 1/4, or more, to desired consistency. Add more
wine, salt, pepper, etc. to taste. (Optional: add a little cream,
maybe 2 tbsp, at the very end.)