Heat a heavy bottom Dutch Oven over medium high heat and add the oil. Once hot, add the onions and ginger and sauté for 4-5 minutes until starting to caramelize. Stir in the broth, soy sauce, lemongrass, star anise, garlic, chicken thighs, cilantro, coriander seeds and peppercorn. Bring to a boil and then reduce to a simmer, with the lid on, and cook for about 20 minutes until the chicken is fully cooked. Remove the chicken to a cutting board and strain the solids from the liquid and put the liquid back into the Dutch Oven.