01 - Boil the diced potatoes in salted water until fork-tender, approximately 15 minutes. Drain and let cool slightly.
02 - Mash the potatoes thoroughly in a large mixing bowl. Incorporate the egg, flour, salt, and white pepper until a soft dough is formed. Add additional flour as needed for easy handling.
03 - On a floured surface, roll the dough into 1-inch balls. Arrange dumplings on a floured tray and set aside.
04 - Melt butter in a large pot over medium heat. Add onion, carrots, and celery; sauté for 5 minutes until softened.
05 - Stir in the minced garlic and cook for 1 minute until aromatic.
06 - Pour in vegetable broth, add bay leaf and dried thyme. Bring to a gentle simmer.
07 - Carefully drop shaped potato dumplings into the simmering soup. Cook for 10 to 12 minutes, or until dumplings float and are cooked through.
08 - Add ground black pepper, pickle brine, chopped dill pickles, and salt to taste. Allow the soup to simmer for an additional 5 minutes.
09 - Remove from heat. Stir in sour cream and freshly chopped dill. Adjust seasoning if necessary, and serve hot, garnished with additional dill if desired.