Add the dried mushroom mix to a bowl and pour the hot water over the top (to reconstitute).
Add the olive oil and butter to a large pot on medium heat, then add in the mushrooms and sauté for about 5 minutes. Remove the mushrooms and their juices and transfer to a bowl.
Add in the minced onion into the pot with some olive oil and cook for another 2 minutes.
Add the white wine, reconstituted dried mushrooms and the wonderful juices they produced to the pot. Add the sautéed mushrooms back in along with the most of the lemon thyme.
Add in the chicken stock and simmer for 15 minutes. Scoop out a few mushrooms (for garnish) and set aside. Add in the heavy cream and cook another 2 minutes.
Using an immersion blender, puree most of the soup, leaving some chunks of mushrooms. This should thicken the soup nicely, but won't leave it too thick or too thin. Serve with a few of the mushrooms pieces and a sprinkling of the reserved lemon thyme.