In a large pot, combine chicken broth, soy sauce, sriracha, and sesame oil. Bring to a simmer over medium heat.
Season the chicken thighs with garlic powder, onion powder, salt, and pepper. Add the chicken to the pot and cook for about 10-12 minutes, or until fully cooked. Remove the chicken and let it rest for a few minutes before slicing.
In the same pot, add ramen noodles and cook according to package instructions, usually about 3-4 minutes.
While the noodles are cooking, prepare the creamy garlic sauce. In a small saucepan, combine heavy cream, minced garlic, and lemon juice. Heat over low, stirring until warmed through.
Once the noodles are cooked, add the baby spinach to the pot and stir until wilted.
Serve the ramen in bowls, topped with sliced chicken, creamy garlic sauce, sliced green onions, and sesame seeds.