Heat butter and olive oil in a pot over medium heat. Add the onion and cook until soft and fragrant.
Add the garlic and mushrooms. Sauté until the mushrooms release their juices and start to brown.
Pour in the vegetable broth and bring to a gentle boil. Let it simmer for about 10 minutes.
Reduce heat and stir in the Hüttenkäse and cream. Use an immersion blender to partially blend the soup, keeping some texture.
Season with salt and pepper, taste, and adjust as needed.
Serve hot with a sprinkle of fresh parsley and maybe a slice of crusty bread on the side.