01 - Melt butter with olive oil in a large heavy-bottomed pot over medium heat. Add the diced onion and sauté until translucent and softened, about 3 to 4 minutes.
02 - Add the minced garlic and sliced mushrooms to the pot. Cook for 8 to 10 minutes, stirring occasionally, until the mushrooms are deeply golden brown and their released moisture has evaporated.
03 - Stir in the dried thyme, salt, and black pepper, coating the mushrooms evenly.
04 - Pour in the vegetable broth and bring to a gentle boil. Reduce the heat to low and simmer uncovered for 15 minutes to allow the flavors to meld.
05 - For a smoother consistency, use an immersion blender to purée the soup directly in the pot to your preferred texture, leaving some pieces if desired.
06 - Stir in the heavy cream and warm gently over low heat for 2 to 3 minutes. Do not boil. Taste and adjust the salt and pepper as needed.
07 - Ladle the hot soup into serving bowls and garnish with freshly chopped parsley. Serve alongside crusty bread or garlic toast.