Place the chicken bones in the slow cooker and cover them with 2.5 l (10.6 cups) water.

Char the onion and 3 scallion stalks in a dry frying pan until deeply browned.

Add the charred onion, charred scallions, and half of the fresh ginger to the slow cooker.

Cook the chicken broth on low for 720 min, then strain it through the fine-mesh strainer.

Soak the kombu seaweed in 1 l (4.2 cups) cold water overnight for 480 min.

Heat the kombu soaking liquid in a stockpot until just below a simmer, then remove the kombu seaweed.

Add the bonito flakes and steep them in the hot liquid for 5 min.

Strain the dashi through the fine-mesh strainer and combine it with the chicken broth.

Finely chop the garlic, remaining fresh ginger, and remaining 3 scallion stalks.

Combine the soy sauce, mirin, sake, Moroccan sardines, chopped garlic, and chopped ginger in a saucepan.

Simmer the sardine soy sauce for 10 min, then strain it into a mixing bowl.

Warm the sesame oil in a frying pan and add the chopped scallions and remaining ginger.

Cook the sesame ginger scallion oil for 3 min, then set it aside.

Bring the combined broth to a gentle simmer and stir in the strained sardine soy sauce.

Cook the ramen noodles in boiling water for 3 to 4 min, then drain them.

Warm the gyoza dumplings in the hot broth for 4 to 5 min.

Divide the cooked ramen noodles among 4 ramen bowls and ladle the hot broth over them.

Arrange the veal slices and 3 gyoza dumplings over each bowl.

Drizzle each bowl with the sesame ginger scallion oil and serve immediately.