adapted from Bon Appétit Magazine, January 2018
Night before: Pour the water into a big bowl and add the kombu. Leave out at room temperature overnight.
Season pork roast with salt and pepper. Tie with kitchen twine at 2" intervals (this helps keep the meat intact while cooking and makes for round, compact slices). Heat oil in large, heavy pot (at least 8 quart capacity). Brown the pork roast on all sides. Add the chicken pieces, spareribs, scallions, carrots, garlic, ginger, and bonito flakes.
Remove the kombu from the dashi and discard. Add the kombu dashi to the meat pot and bring to boil. Reduce heat to maintain a slow simmer and cook for 2 1/2–3 hours, uncovered. The liquid will reduce to about 2 quarts, leaving a concentrated and flavorful broth.
Remove pork roast from the broth and let cool. Wrap tightly in plastic wrap and chill until ready to use.
Strain broth into another large bowl and discard solids. (I usually pull the remaining meat off the bones of the ribs and chicken to feed to my dog, which makes her very happy.) Cover and chill until ready to use.
Combine the soy sauce, sake and mirin in a small jar or bowl.
Soft cook the eggs. Bring a pan of water to boil, using a slotted spoon, lower in the eggs and boil gently for 6 1/2 minutes. Transfer eggs to a bowl of ice water for a couple minutes to stop the cooking. Peel and set aside. (Eggs can be cooked up to 3 days in advance, store in an airtight container in the refrigerator.)
Reheat broth. Bring broth to a simmer. Add the tare and keep warm without boiling.
Remove twine from roast and slice the pork into thin rounds. Set out on cutting board or plate along with other toppings (green onions, bamboo shoots, nori). Cut the eggs in half so they're ready to go.
Boil a big pot of water for the ramen noodles and cook to al dente; drain.
Divide ramen among 6 deep bowls. Top with sliced pork. Ladle broth over the ramen and pork. Add egg halves, green onions, bamboo shoots, and tuck the nori along the side of the bowl. Serve ramen with chile oil, sesame oil, sriracha, and/or other condiments you like. (Shichimi togarashi is recommended, but I haven't found any yet.)