Blanch beef in boiling water then drain. In a clean pot, add beef, water, spices and seasonings. Bring water to a boil then leave to simmer for 1-1.5 hours.
When completely cool, place beef and broth (discard spring onion, ginger, spices and the fat floating on the surface if there is any) in separate containers. Store in the fridge for at least 1 hour (see note 1).
Cook soba noodles according to the instructions on the package. Drain and rinse under running water to cool fully.
Meanwhile boil egg. Peel and halve it.
Pour cooled broth into two large serving bowls. Add vinegar, sugar and salt. Cut the beef into thin slices (see note 2).
Place the noodles into two bowls. Top with beef, egg, apple, cucumber, kimchi and red chilli paste. Sprinkle sesame seeds over.