Combine carrots, chicken broth, and onion in a large pot.
Pour enough water into the pot to assure the ingredients are covered; add garlic, thyme, and tarragon.
Bring the liquid to a boil, reduce heat to medium-low, place a cover on the pot, and simmer the mixture until the carrots are very tender, 40 to 50 minutes.
Remove pot from heat and cool soup for 10 minutes. Puree soup with an immersion blender or mash vegetables with a potato masher and whisk the soup until smooth.
Return pot to medium heat and cook until reheated, about 5 minutes. Stir cream through the soup.
