In a 4- to 5-quart pot, add the boneless skinless chicken thighs, garlic, ginger, scallion whites, kosher salt, freshly ground pepper, and water. Stir everything together.

Bring the mixture to a boil over high heat. Once boiling, reduce the heat to medium-low and let it simmer uncovered for about 15 minutes, stirring occasionally, until the chicken is tender.

While the soup is simmering, whisk together black rice vinegar, soy sauce, and toasted sesame oil in a bowl. Add crispy chili oil if desired.

Carefully remove the chicken thighs from the pot and shred them with forks.

Add the dried ramen noodles and carrot matchsticks to the pot. Cook for about 3-4 minutes until the noodles are tender.

Return the shredded chicken to the pot and gently stir for 1 minute to rewarm.

Adjust the seasoning as needed, then divide the soup among bowls. Top with reserved scallion greens and drizzle with the prepared sauce before serving.