Take 300 g duck breast and pat the surface dry with kitchen paper.
Make shallow diagonal incisions on the fat about 0.5cm apart, then repeat in the opposite direction to score.
Sprinkle with a pinch of salt and pepper on both sides.
Take a cold frying pan and place the duck inside with the skin-side facing down. Place the pan to the stove and turn on the heat to medium. Fry for 4 minutes. (Electric stoves take a bit longer to heat up so if you use electric stove, increase the cooking time accordingly.)
Flip it over and fry on the other side for 30 seconds.
Remove the duck breast from the pan and wrap it in foil. Leave it to rest for 3 minutes.
Return the pan to the stove and heat it on medium. Once hot, place the duck breast back into the pan with the skin side down. Fry for 3 minutes while basting the surface with the excess fat and juices in the pan.
Once 3 minutes are up, flip it over and fry on the other side for 30 seconds again.
Remove from the pan and wrap it in the aluminum foil once again. Rest it in the foil until it's time to cut and serve.
Cook 4 portions soba noodles according to the instructions on the packaging.
Pour the excess duck fat into a heatproof container and add the 100 g Japanese leeks (naganegi) cut into 5cm pieces to the pan. Fry until lightly charred all over.
Add the 1000 ml dashi stock, 40 ml dark soy sauce, 40 ml light soy sauce, 100 ml mirin and 2 tsp sake to the pan with the leeks and bring to a boil. Bubble for 1-2 minutes to cook off the alcohol in the mirin and sake.
Thinly slice the duck breast and divide the cooked soba noodles into serving bowls. Pour the broth over the top and place 2-3 pieces of leeks and 2-3 slices of duck breast to each bowl. Sprinkle with chopped green onion, shichimi (optional).
Enjoy!