In a large pot, combine the chicken broth, water, garlic, ginger, soy sauce, and miso paste (if using). Bring to a boil over medium-high heat.
Add the chicken thighs to the pot and reduce the heat to medium. Simmer for about 20 minutes or until the chicken is cooked through and tender.
Once the chicken is cooked, remove it from the pot and shred it using two forks. Set aside.
In the same pot of broth, add carrots and ramen noodles. Cook according to the package instructions, about 4-5 minutes, or until noodles are tender.
During the last minute of cooking, stir in the baby spinach and sliced green onions.
Taste the broth and adjust seasoning with salt as needed.
Divide the cooked ramen noodles, vegetables, and shredded chicken into serving bowls. Ladle the hot broth over the top.
Garnish each bowl with halved boiled eggs, sesame seeds, and cooked corn if desired.