While I relied on wild birch boletes and store-bought cremini mushrooms here, you can really use any mushroom you'd like. Each one will make the bisque a bit different, and you will ultimately come up with your own blend that suits your taste, your time, and your place. Whatever green garnish you choose, please use something. I find that the bisque gets disturbingly like gravy if you don't have something bright and green in it. And while yes, this is vegetarian, feel free to use chicken or beer or wild game broths in its place.
3tablespoonsunsalted butter,plus one more tablespoon
1poundfresh mushrooms,minced (save aside a few nice mushrooms for garnish)
1large yellow or white onion,minced
1/3cupsherry or brandy
Salt(smoked salt if you have it)
2to 4 tablespoons heavy cream
Chives,parsley or some other green herb to garnish
Lots of black pepper
Break the dried mushrooms up and soak them in the hot water for 45 minutes to an hour. Chop fine once they're soft. Save the soaking water and strain it through a paper towel to remove debris and dirt.
Heat 3 tablespoons of butter in a soup pot and cook the onions and mushrooms over medium heat, stirring occasionally, until they start to brown, about 10 minutes.
Add the reconstituted mushrooms to the pot, stir well and cook another minute or three. Add the sherry, a healthy dash of salt and the thyme. Stir well and scrape off any browned bits from the bottom of the pot.
Add 4 cups of the soaking water and bring to a simmer. Cook gently for 20 t0 30 minutes.
Meanwhile, slice the garnish mushrooms and saute in the remaining tablespoon of butter until nicely browned. Set aside.
Ladle about 1/3 to 1/2 of the soup into a blender and puree. Chances are it will seize up and be too thick, so add the remaining soaking water to loosen things up. Return this to the pot, stir well and add some water if you think it's too thick. Return to a simmer.
To serve, stir in some heavy cream and lots of black pepper. Ladle into bowls and garnish with the sauteed mushrooms and herbs.
Once made, this bisque will keep in the fridge a week. It doesn't freeze very well once it has the cream in it, so if you make a big batch to freeze, skip the cream until you plan to eat it.