1. Preheat oven to 350 degress Fahrenheit (180 degrees Celsius).
2. Saute onions in oil in a large skillet until caramelized. Add in one cup stewed plums, soy sauce, mustard, garlic, ginger, garlic powder, and pepper. Let it all reduce together for about 10 minutes over medium heat.
3. Arrange chicken pieces (I prefer skinned, but you can keep the skin on if you’d rather) in a baking pan. Pour plum sauce over chicken and bake, covered, for one and a half hours, or until the chicken is very tender.