Clean and slice the mushrooms. Dice the onion and mince the garlic.

Heat olive oil in a pot over medium heat. Add chopped onion and cook until translucent, about 3 minutes.

Add garlic and thyme; cook for another minute. Then add sliced mushrooms and cook until tender, about 5 minutes.

Pour in vegetable broth and bring to a boil. Lower heat and simmer for 10 minutes.

Use an immersion blender to puree the soup until smooth. Stir in skim milk and season with salt and pepper.

Serve hot, garnished with a few fresh thyme leaves if desired.