Soak the dried porcini mushrooms in about 1 1/2 cups of hot water. Cover with a small plate or another bowl to keep them submerged. Soak for about 15 minutes or until they are soft. Drain through a fine sieve reserving the liquid. Once they cool, chop them into smaller pieces. Set aside.
Clean the fresh mushrooms by brushing with a mushroom brush if you have one or wipe them with dry paper towels. Separate the
stems, trimming off any bad parts. Coarsely chop the stems. Slice the
mushroom caps 1/4-inch thick and if the mushroom are really large (like the portobello) cut those into smaller bite-sized pieces. Set aside.
Heat the the oil and 1 tablespoon of butter in a large stock pot. Add
the hydrated porcini mushrooms, chopped fresh mushroom stems, the onion, carrot, the sprig of thyme, 1
teaspoon salt and 1/2 teaspoon of pepper, and cook over medium-low heat
for 10-15 minutes, until the vegetables are soft. Add the reserved water from the dried mushrooms plus enough extra water to make 6 cups of water total. Bring to a boil, reduce the heat and simmer uncovered for 30 minutes.
Strain, reserving the liquid. You should have about 4 1/2cups of stock.
If not, add some additional water.
Meanwhile, in another large
pot, heat the remaining 5 tablespoons of butter and add the leeks. Cook
over low heat for 15-20 minutes, until the leeks begin to brown. Add
the sliced mushroom caps and cook for 10 minutes, or until they are
browned and tender. Add the flour and cook for 1 minute. Add the white
wine and stir for another minute, scraping the bottom of the pot. Add
the mushroom stock, minced thyme leaves, 1 teaspoon of salt and 1
teaspoon of pepper and bring to a boil. Reduce the heat and simmer for
15 minutes. Add the half-and-half, cream and parsley, season with salt
and pepper to taste, and heat through but do not boil. Serve hot.
Ladle soup into to large bowls and sprinkle a little fresh parsley on top of each bowl. Serve right away. We served ours with warmed crustry French Bread.