Make the chicken stock for the ramen. Rinse the chicken bones and place them in a large pot covered with water. Bring to a boil over high heat and continue to simmer for 10 minutes. Remove from heat and drain the chicken bones, rinsing the bones and pot. Place the chicken bones back in the pot with 8 cups of water, ginger, garlic, and 3 stalks of green onion. Cover the pot, bring to a boil, reduce heat to low, and simmer for 2 hours. Skim the fat and keep warm.
Meanwhile, make the chashu pork. Combine the pork belly with sake, soy sauce, mirin, water, sugar, ginger, garlic, and the stalk of green onion. Cover the pot and bring it to a boil. Reduce heat to low and continue to simmer for 2 hours or until the pork is fall-apart tender.
Make the tare. Combine all ingredients for the tare in a small saucepot and bring to a boil over medium heat. Reduce heat to low and simmer for 5 minutes. Strain, discarding ingredients. Let cool.
Assemble the ramen. Cook the noodles and drain. Pour 1 tablespoon tare, 2 cups chicken broth, and 1 teaspoon MSG per bowl. Add the noodles, thinly shaved onion, radish sprouts, scallions, and a boiled egg. Serve immediately.