salt and freshly ground black pepper to taste
1 tablespoon vegetable oil
1 large onion, sliced
8 cloves garlic, minced
1 1/2 cups chicken broth
1 cup seasoned rice vinegar
1/2 cup soy sauce, or to taste
2 teaspoons sambal chili paste, or other hot pepper sauce to taste
2 bay leaves
Season duck legs with salt and black pepper. Heat vegetable oil in a large, deep skillet over medium-high heat; add duck legs, skin side down, and cook until browned, 3 to 4 minutes per side. Remove duck legs and drain all but 1 tablespoon of duck fat from the pan. Cook onion in reserved duck fat over medium heat until onion begins to turn translucent, 3 to 4 minutes. Add garlic; cook and stir until fragrant, 1 to 2 minutes. Stir chicken broth, rice vinegar, soy sauce, sambal chili paste, and bay leaves into onion mixture; bring to a simmer. Return duck legs to the skillet, loosely cover, and simmer until duck legs are tender and easily pierced with a fork, about 2 hours. Remove cover from the skillet, increase heat to high, and cook until sauce is thick, about 5 minutes; season with salt and black pepper to taste.