Preparation:

Step 1:
Season the chicken thighs generously with salt and pepper on both sides. Heat a large skillet over medium heat and add the vegetable oil. Once the oil is hot, place the chicken thighs in the skillet, skin-side down, and brown them for about 5 minutes on each side, until they are golden and crispy. Set the browned chicken aside on a plate.

Step 2:
In the same skillet, without cleaning it, add the minced garlic and ginger. Sauté the mixture for about 1 minute, until it becomes fragrant and lightly golden. Be careful not to burn the garlic, as it will turn bitter.

Step 3:
Add the soy sauce, chicken broth, rice vinegar, brown sugar, and sesame oil to the skillet. Stir the mixture to combine all the ingredients and allow the flavors to meld together. Make sure to scrape the bottom of the skillet to incorporate the browned bits left from the chicken, as they add rich flavor to the sauce.

Step 4:
Return the browned chicken thighs to the skillet, placing them skin-side up. Reduce the heat to low, cover the skillet with a lid, and let the chicken simmer gently for about 30 minutes. During this time, the chicken will become tender as it absorbs the delicious flavors of the sauce.

Step 5:
After 30 minutes of simmering, add the green onions to the skillet, distributing them evenly around the chicken thighs. Cook for another 5 minutes, allowing the green onions to soften and infuse their flavor into the dish. At this point, if you prefer a thicker sauce, mix the cornstarch with a tablespoon of water and stir it into the sauce. Let it simmer for an additional 2 minutes, or until the sauce reaches your desired consistency.