Bake two of the potatoes—we like to bake ours this way, starting them in the microwave. When they are cool enough to handle, cut them in half. Scoop out the flesh and reserve it. Reserve the baked skin, too—don’t throw it out or, if you are me, don’t just sit down and eat it with a bunch of salt. Meanwhile, take the other 3 potatoes, the raw ones, peel them and cut into 1-inch cubes.
Heat the olive oil in a heavy medium-sized saucepan. Add the carrots and celery and sauté for three minutes. Add the onions and sauté another two minutes. Then add the garlic and sauté another minute.
Add the raw potato cubes and enough water (or water and stock) to cover—I used 3 cups. Bring to a boil, reduce to a simmer and cover.
After six or seven minutes, take half of the baked potato and add to the simmering soup. Coarsely chop the baked potato skin and put it into your blender.
Cook the soup until the potato cubes are cooked through (but not mushy soft).
Cool for about 15 minutes. Put about 2/3 of the soup in the blender along with the baked skins and whirl until everything is smooth. (Make sure to reserve some of the solids! One of the nice things about this soup is that it is smooth AND chunky.) If the puréed soup is too thick, more like a paste than a soup, then add a little water or stock. Then return it to the saucepan and stir everything together.
If you intend to let the flavors mellow overnight, cover the soup and refrigerate it.
If you intend to serve it right away, start heating it. When it is heated to your taste, carefully add in 1/2 cup of sour cream, gently whisk together and salt to taste.
Ladle it into bowls and add your preferred garnishes. We used a modest amount of very sharp cheddar cut into small cubes and the fresh chives. We really did not feel the need to include bacon or other garnishes.
If you refrigerate soup that already has sour cream in it, reheat it gently so the sour cream will not break.