Heat olive oil in a large pot over medium heat. Add onion and cook until softened, about 5 minutes.

Add carrots and cook for another 5 minutes, stirring occasionally.

Pour in vegetable broth and bring to a boil. Reduce heat and simmer for 20-25 minutes, or until carrots are tender.

Carefully transfer soup to a blender (or use an immersion blender) and blend until smooth.

Return soup to the pot and stir in heavy cream, butter, and thyme. Season with salt and pepper to taste.

Heat through and serve.