Melt butter in dutch oven or soup pot over medium high heat. Add onion blend (or just onion) and sauté until onion is tender, about 5 minutes.
Pour in chicken broth and frozen veggies. Bring this just to a boil and then reduce heat to a simmer until veggies are tender, about ten minutes. Add in heavy cream, parsley, salt, and pepper. Stir well and continue to simmer.
To thicken with Glucomannan: In a measuring cup, stir 1 teaspoon of Glucomannan into a cup of cold water until dissolved. Stir this into the soup and continue to simmer for about ten minutes more, stirring from time to time.
To thicken with flour: Stir one tablespoon of flour into one cup of water and then stir into soup. Continue to simmer for about ten minutes, stirring from time to time.