In a large pot, heat the olive oil and butter over medium heat. Add the chopped onion, carrots, and celery. Sauté for about 5-7 minutes, or until the vegetables are softened.

Stir in the thyme, parsley, salt, and black pepper. Cook for an additional minute until fragrant.

Pour in the chicken or vegetable broth and bring the mixture to a boil. Reduce the heat and let it simmer for 15 minutes.

While the soup is simmering, prepare the roasted garlic. Squeeze the roasted garlic cloves out of their skins and set aside.

After the soup has simmered, add the roasted garlic and heavy cream. Use an immersion blender to puree the soup until smooth, or carefully transfer it to a blender in batches.

Stir in the lemon juice and adjust seasoning if necessary. Heat through for an additional 5 minutes.

Serve hot with crusty bread on the side.