The reason for adding the liquid from soaked dried mushrooms to the sauce is to enhance the flavor of the mushrooms. What used to be called wild mushrooms are now called exotic because they really are grown domestically — not foraged in the wild.
Place the dried mushrooms in a small bowl and pour over the hot water. Let sit for 10 minutes.
Place the chicken stock in a small saucepan and cook over a gentle heat until reduced by one-third. Drain the porcini liquid into the chicken stock, except for the last tablespoon which my be sandy. Chop the reconstituted porcini into 1/4-inch dice.
To make the mushroom mixture, brush and trim a selection of fresh wild and domestic mushrooms (shitaki, oyster, chanterelle or morels). In a medium skillet melt the butter and cook the shallot until soft. Add the chopped wild and fresh mushrooms and cook gently until they release part of their moisture. At this point add the brandy and cook a minute more. Then add the herbs (thyme, tarragon, chives or parsley). Add the cream, then the reduced chicken stock, and salt and pepper to taste.
In a large heavy pot, bring 4 quarts of water to a boil, add 1 Tbs. salt, add the pasta being careful that it doesn’t stick together. Simmer, stirring with a wooden fork until the pasta no longer tastes of raw starch when tasted. Immediately drain the pasta, saving 1 to 2 cups of the cooking water. Put the drained pasta back into the pot, toss with the exotic mushroom sauce, taste and adjust the seasoning. If the pasta seems to be drying out, stir in some of the cooking liquid. Serve immediately on warmed plates.