In a large pot, bring 10 cups of water to a roaring boil over high heat. Add chicken thighs, sliced garlic, chopped ginger, scallion whites, salt, and pepper. Stir gently to combine all ingredients, then cover the pot and let it boil before reducing the heat to medium-low. Allow it to simmer for about 20 minutes until the chicken is tender.

Carefully remove the chicken thighs from the pot using tongs. Let them cool on a cutting board.

Using two forks, shred the chicken thighs into bite-sized pieces. Set aside while maintaining the pot of simmering broth.

Add the dried ramen noodles and matchstick carrots into the simmering broth. Stir occasionally to prevent sticking. Cook according to package instructions, usually around 4 to 5 minutes.

Once the noodles are cooked, lower the heat and stir in black rice vinegar, soy sauce, and sesame oil. Adjust seasoning as needed.

Return the shredded chicken to the pot. Stir gently to combine and warm through. Ladle the soup into bowls, garnish with reserved scallion greens, and drizzle with crispy chili oil if desired. Serve warm.