In a large pot over medium heat, add the carrots, celery, onion, and olive oil. Cook for 10 minutes until the onions are translucent, stirring occasionally and adding a bit of water to prevent burning (a bit of browning is fine).
Add the cornstarch and diced potatoes, and stir well. Then add the garlic powder, thyme, and 4 cups of vegetable broth.
Stir, cover and bring to a boil.
Meanwhile, place the vegan sour cream in a small mixing bowl.
Once the soup is boiling, lower the heat and add the dry textured vegetable protein, nutritional yeast, vegan worcestershire sauce, kosher salt, and dried tarragon.
Cook covered at a gentle simmer for approx 15 minutes until the potatoes are fork tender (stir around halfway through).
Then turn off the heat and take about two cups of the broth and slowly whisk it into the vegan sour cream, to slowly bring up the heat of the sour cream.
Transfer the sour cream mixture back into the pot and stir well. Add the remaining cup of vegetable broth if desiring a thinner texture and check for seasoning.
Serve and top with the chives and cayenne to taste.