In a large pot, combine broth, potatoes, carrots, butter and bay leaf. Bring to a boil and cook until the potatoes are tender, about 15 minutes. Remove the bay leaf.
Combine the pickle juice, water and flour. Whisk together to create a slurry. Add it to the pot, along with the pickles and salt and pepper. Simmer for 5-10 minutes, until thickened.
Ladle half of the soup into a blender and process until smooth. Add back to the pot along with the yogurt and stir to combine.
Serve immediately garnished with fresh dill, and additional yogurt and chopped pickles if desired.