Gather the ingredients.
Melt butter in a large pot. Sauté the onion until translucent, about 3 minutes.
Add broth and potatoes. Bring to a boil, reduce heat, and simmer until potatoes are tender, about 15 minutes. Add the pickles, pickle juice, and salt. Cook for 5 minutes more.
In a small bowl, blend flour with sour cream.
Temper the sour cream mixture by whisking in a little hot soup, so it does not curdle.
Pour tempered sour cream back into the hot soup, whisking constantly, until it comes to a boil. Reduce heat to low and simmer 3 minutes, or until slightly thickened.
Adjust seasoning with salt and pepper, and optional sugar.
At this point, the soup can be left chunky or puréed to the velvety consistency of vichyssoise .
Serve in heated bowls garnished with fresh dill and accompanied by hearty rye bread.
