In a large pot, heat the vegetable oil over medium-high heat. Add the chicken pieces and cook until browned and cooked through, about 5-7 minutes. Remove the chicken from the pot and set aside.
In the same pot, add the minced garlic and ginger, sautéing for about 1 minute until fragrant.
Pour in the chicken broth, soy sauce, miso paste, and sriracha. Stir well to combine and bring to a simmer.
Add the ramen noodles to the pot and cook according to package instructions, usually about 3-4 minutes.
Once the noodles are cooked, return the chicken to the pot and add the baby spinach. Stir until the spinach is wilted, about 1-2 minutes.
Serve the ramen in bowls, topping each with sliced green onions and a soft-boiled egg if desired. Sprinkle with sesame seeds for garnish.