Place marrowbone in cold water for about 1/2 hour. Clean and wash the vegetables and cut them into very fine strips. Press out marrow, warm up while stirring until it becomes smooth. Add breadcrumbs, egg, salt and pepper, mix well and let it rest for about 10 minutes.
Form into small balls. Let the dumplings simmer in hot broth for 5-8 minutes. Results in about 20 dumplings.