Potato, Kale, and Sausage Soup

I made a soup yesterday, that is so transcendently delicious that I can hardly believe I made it.  It's a riff on a recipe that I got from a CSA (farm share) cookbook many years ago that is an old favorite of mine.  I'm a pescatarian (no meat expect fish), so I made this with veggie sausage, but I'm sure it would taste good with regular sausage too if that is more your style. The balsamic vinegar is really what gives this soup sparkle, so be sure to add it even if it sounds like a weird addition!

Potato, Kale, and Sausage Soup
olive oil
2 full-size veggie sausages, chopped into rounds (I used Field Roast Italian Style sausage)
1 large onion, diced
3 carrots, chopped
3 stalk celery, chopped
5 medium yellow potatoes, chopped
4 bouillon cubes
8 cups water
1 large bunch kale, torn into pieces
black pepper
balsamic vinegar

Before you begin, put on a kettle of hot water to heat. Heat a little oil in a soup pot. Add the sausage rounds and cook until done. It's ok if some sticks to the pan- it will help give the soup flavor. When the sausage is done, transfer it to a small bowl and set aside. Heat a bit more oil, and cook the onions until they are almost translucent. Add the carrots and celery and cook until celery is softened. Add potatoes and a little water from your kettle to keep the veggies from sticking. Stir. Using the heated water, dissolve the bouillon cubes in a small bowl. Stir dissolved bouillon into soup pot and add water (approximately 8 cups).  Bring to a boil and then reduce heat. Cook for 15 minutes, or until potatoes and carrots are tender.  Add kale pieces and some black pepper. Stir and cook for 5 more minutes. Stir in sausage and a few splashes of balsamic vinegar. Serve.  Tastes even better the second day!