01 - Melt butter with olive oil in a large soup pot over medium heat. Add the chopped onion and cook, stirring occasionally, until softened and translucent, 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 browned and most of 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 boil. Reduce the heat to low and let the soup simmer gently for 15 minutes to develop the flavors.
05 - For a smoother, creamier consistency, use an immersion blender to purée the soup to your preferred texture. Skip this step if you prefer a chunky, rustic soup.
06 - Stir in the heavy cream and heat gently over low for 2 to 3 minutes. Do not let it boil. Taste and adjust the salt and pepper as needed.
07 - Ladle the soup into warm bowls and garnish with chopped fresh parsley. Serve immediately with crusty bread or garlic toast on the side.