Make chicken stock. Rinse 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, rinsing bones and the pot.
Place chicken bones back in the pot with water, ginger, garlic, and 3 stalks of green onion. Cover the pot and bring to a boil. Reduce heat to low, and simmer for 2 hours. Skim fat and keep warm.
Meanwhile, make chashu pork. Combine pork belly with sake, soy sauce, mirin, water, sugar, ginger, garlic, and the stalk of green onion. Cover the pot and bring to a boil. Reduce heat to low and continue to simmer for 2 hours or until pork is fall-apart tender.
Make shoyu tare. Combine all ingredients for 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 ramen. Cook noodles and drain. Pour 1 tablespoon tare, 2 cups chicken broth, and 1 teaspoon MSG per bowl. Add noodles and top with chashu, soft boiled egg, and scallions. Serve immediately.
Notes
The chicken broth, chashu pork, and shoyu tare can all be prepared the day before.You can top the ramen with additional garnishes such as corn, nori, bamboo shoots, and fish cake.You can skip the msg, but it does add a savory element that's commonly found in ramen and cannot be substituted with another ingredient.