Heat olive oil in a large pot over medium heat.
Add chopped onions and sauté until translucent.
Stir in minced garlic and cook for an additional minute.
Add sliced mushrooms and cook until they release moisture and become soft.
Season with salt, pepper, and optional herbs.
Pour in the vegetable broth and bring to a simmer.
Cook for 15 minutes to allow flavors to meld.
Use an immersion blender to puree the soup until smooth.
Stir in heavy cream and heat through without boiling.
Serve hot, garnished with fresh parsley and sliced mushrooms.