In a large pot, heat the sesame oil over medium heat. Add the chicken thighs and cook for 6-7 minutes on each side until golden brown and cooked through. Remove from the pot, let it rest for a few minutes, then slice into thin strips.
In the same pot, add the minced garlic and grated ginger, sautéing for about 1 minute until fragrant. Pour in the chicken broth and bring it to a gentle simmer.
Stir in the soy sauce and sriracha, adjusting the level of spice to your preference. Allow the broth to simmer for an additional 5-10 minutes to let the flavors meld together.
Bring the broth back to a full boil, then add the ramen noodles. Cook according to package instructions, usually about 4-5 minutes.
In the last minute of cooking, add the chopped green onions and baby spinach, allowing them to wilt into the broth.
Divide the ramen noodles and broth into serving bowls. Top with slices of chicken and a soft-boiled egg (if using).
Sprinkle with toasted sesame seeds and fresh cilantro for an aromatic finish. Serve hot and enjoy the spicy kick!