SERVES: 4 | PREP TIME:
Place a large saucepan over medium heat. Add the butter followed by the onion, carrot, parsnip, potato, salt, and pepper. Cook until the vegetables begin to soften, about 7 minutes. Pour in the chicken broth and add the 1 teaspoon of fresh chopped thyme and cayenne. Season with salt again, if necessary, and bring to a boil over high heat. Reduce the heat to low and simmer until the vegetables become very tender, about 20 minutes.
Working in small batches in a blender or using an immersion blender, puree the soup until smooth. Strain the soup into a clean large saucepan and stir in 1/4 cup of the warmed cream and more broth, if desired. Check the soup again for seasoning, then heat through. Ladle the soup into 4 bowls, spoon 1 tablespoon of warm cream into the middle each bowl and swirl with a spoon. Top the soup with a sprig of fresh thyme, then serve.