In a large pot, sauté the onion and garlic until translucent.

Add the chopped cabbage and diced potatoes, and stir for a few minutes.

Pour in the vegetable broth, bring to a boil, then reduce heat and simmer for 20 minutes until the vegetables are tender.

Use an immersion blender to puree the soup until smooth, or transfer to a blender in batches.

Stir in the heavy cream and milk, and season with salt, pepper, and thyme.

Serve hot, garnished with fresh herbs if desired.