"This modified version of potato soup is completely vegan and no one can tell a bit of difference. Even picky kids love this hearty recipe, perfect for cold weather or cravings for comfort food. Top with sour cream, Cheddar cheese, green onions (or even bacon, for the meat-eaters out there), or just eat it right out of the pot. Either way, it's delicious."
Melt margarine in a large stockpot over medium heat; cook and stir onions, celery, and carrots until tender, about 10 minutes. Add water, vegetable bouillon, salt, and pepper; stir well. Add potatoes and bring soup to a boil; reduce heat and simmer until potatoes are tender, about 15 minutes.
Mix 4 cups soy milk and instant potatoes into soup until dissolved.
Stir remaining 1/2 cup soy milk and cornstarch together in a bowl until smooth; add to the soup, stirring well. Cook soup until heated through, stirring regularly, 5 to 10 minutes.