This is an easy recipe to make -- if you already have acorn flour. If you don't have your own acorn flour, you can substitute chestnuts. If you can't find dried porcini mushrooms, any dried mushrooms will work. Don't skip the garnishes, however. They add a lot. I especially like the slices of grouse breast. I simply sear skinless grouse breast in butter until it's just barely done, then salt and slice thin. One tip: If you do skip all the garnishes, you can actually use this soup as a gravy for meats if you let it get thick. I prefer it thinner, however, with a consistency like melted ice cream.
Soak the dried mushrooms in the hot water for an hour before starting. Squeeze the moisture from the mushrooms and chop coarsely. Save the water, straining it if there is a lot of debris.
Heat the butter in a soup pot over medium-high heat and saute the carrot, celery and onion until they are soft, but not browned, about 5 minutes. Add the chopped mushrooms and acorn bits and stir to combine. Saute another 2 minutes or so.
Add the brandy and boil it hard until it is almost gone, then add the bay leaves, 2 cups of mushroom soaking water and the stock. Bring to a simmer, taste for salt and add if needed. Cover and simmer gently for 1 hour.
Puree the soup in a blender (or use an immersion blender), then -- if you want to get fancy -- pass it through a fine-meshed sieve. If the soup is too thin, simmer it until you get a soup the consistency of melted ice cream. if it's too thick, add water or stock.
Serve with a drizzle of creme fraiche or sour cream. Add some chopped parsley, a few drops of nice oil (I prefer roasted squash seed oil) and, if you want it to be a main course, a few slices of grouse, partridge, pheasant or chicken breast.
Notes
The soup will hold for several days in the fridge if you want to make it ahead of time.