Prep all the vegetables and grate the pickles. Place a large stock pot over medium heat and add the butter. Once melted, add in the onions. Sauté for 2-3 minutes, then stir in the celery, carrots, and garlic. Sauté for another 5-8 minutes, stirring occasionally.
Once the veggies have softened, add the sliced potatoes, broth, grated pickle, and bay leaf. Bring to a boil and simmer the soup for 20 minutes, or until the potatoes are soft. Remove the bay leaf, and use an immersion blender the puree the soup a little to thicken the base. Do not fully puree.
Remove 1 cup of soup base from the pot. Stir to cool. Quickly whisk in the egg yolks into the small portion of soup. Whisk fast so the yolks incorporate smoothly into the base, not scramble. Then whisk the egg mixture back into the pot. Simmer for 5 more minutes. This gives the entire pot of soup a luxurious silky texture.
Stir in 1 tablespoon dill pickle juice and fresh dill. Taste, then add more pickle juice if desired and salt and pepper as needed.
NOTES: 1) The pickles, pickle juice, and broth add salt to the soup. Do not salt unless needed at the end. 2) If you don't have an immersion blender, you can thicken the soup by placing 2 cups of soup in a standard blender. Open the vent in the lid and cover the blender. Then cover the lid with a kitchen towel for safety. Puree the soup and stir back into the pot.