How to Make It
In a large stockpot, combine the chicken, ribs, leek, ginger, garlic, water and shoyu. Bring to a boil.
Meanwhile, in a skillet, heat the oil. Season the pork butt with salt and brown it well on all sides over high heat, 12 minutes; transfer to the stockpot. Simmer the broth over moderately low heat for 2 hours, until the pork butt and ribs are just tender; skim any scum that rises to the surface. Transfer the pork butt and ribs to a platter and refrigerate. Strain the broth and discard the remaining solids.
Return the broth to the pot. Add the kombu and simmer over moderately low heat for 1 hour and 30 minutes. Let cool, then chill and refrigerate the broth overnight.
Preheat the broiler. Skim the fat off of the broth and discard the kombu. Bring the broth to a simmer. Season with shoyu and keep hot.
Untie the pork butt and slice it across the grain 1/3 inch thick. Cut the ribs between the bones. Arrange the pork slices and ribs on a large baking sheet and brush with shoyu. Broil 8 inches from the heat for 3 minutes, turning once, until the meat is crisp; keep warm.
Divide the cooked noodles among 8 bowls and ladle 1 1/2 cups of broth into each one. Add the spinach in piles. Drain the eggs, cut each one in half lengthwise and set a half in each bowl. Arrange 2 slices of pork butt and 1 rib in each bowl and garnish with the scallions and nori. Serve the ramen immediately, passing the rice vinegar and togarashi at the table.
Variations Stir 1/2 teaspoon white miso, 1/2 teaspoon Madras curry paste or 2 teaspoons coarsely ground toasted sesame seeds into each serving of broth before adding the toppings.