Bring half a pot of water to boil. Add pork bones and allow it to continue boiling for 5 minutes. Remove bones with thongs. Rinse of scum if any. Discard water and rinse the pot.
Fill pot with 10 cups (2.4 liters) of water. Bring it to a boil. Add ginger and return pork bones to the pot. When it comes to a boil, reduce heat and allow it to simmer for 2 hours.
Teriyaki Pork Tenderloin
Combine soy sauce, mirin, brown sugar, and ½ cup (120ml) water in a bowl.
Heat vegetable oil in a deep fry pan. Brown pork tenderloin on all sides, about 5 minutes.
Pour sauce into the pan. Cover, reduce heat to medium low and allow pork tenderloin to cook for 30 minutes, turning once half way through. Do keep an eye on it as sauce may darken and thicken. If needed, add another ¼ cup (60ml) water so that it does not burn.
When done, remove pork tenderloin from pan. Cut into thin slices when cool enough to handle.
Buttered Corn Kernels
Melt butter in a small saucepan. Add corn kernels and cook for 3 minutes. Remove and set aside.
Garlic Chili Oil
Combine garlic, pepper flakes, and vegetable oil in a small microwavable dish. Microwave on high for approximately 1½ minutes. Remove and set aside.
Cook Bean Sprouts and Noodles
Bring a large pot of water to boil. Lightly scald bean sprouts for about 20 seconds. Remove with slotted spoon. Set aside.
Add ramen and cook as per packaging instructions. Drain and rinse under cold water. Add sesame oil. Toss to coat.
Divide noodles into 4 bowls. Top each bowl with slices of teriyaki pork tenderloin, some scalded bean sprouts, buttered corn kernels, and chili bamboo shoots (if using).
Put shiro and aka miso in a medium sized bowl. Pour 1 cup (240ml) of boiling stock over miso. Stir to melt miso. Set aside.
In a large pot, heat 2 tablespoons vegetable oil. Add sliced green onions and fry for 2 minutes.
Pour in 8 cups (1.8 liters) stock. When stock comes to a boil, reduce heat to minimum setting.
Gently pour melted miso back into pot. Do not allow soup to come to a boil. Turn off heat.
Putting it together
Finally, pour miso soup over noodles and toppings in each bowl. Sprinkle with sliced green onions and drizzle with garlic chili oil.