Heat oil in large skillet (or electric frying pan) to medium-high.
Salt and pepper chicken thighs on both sides.
When oil is hot, place chicken thighs in the pan, skin side down, and brown for 8-10 minutes—turn chicken over and brown the other side.
In a 2-cup measure, combine the brown sugar, soy sauce, minced garlic and enough boiling water to total about 1 cup.
Remove chicken from frying pan and discard the liquid left in the pan but don’t wash the pan. (Tip: never pour hot oil down the sink, it hardens and clogs the pipes.)
Pour the contents from the measuring cup into the frying pan and place back on medium-high heat. When the liquid starts to boil, place chicken back into the pan, skin side down. Allow to continue bubbling for 5 minutes then add green pepper, if using.
Turn heat down to low or medium-low, cover and simmer for 45 minutes, turning chicken every 15 minutes. (Remove lid for the last 5-10 minutes of cooking.)
Remove from heat and allow to stand, lid off, for 5 minutes before serving.
Serve with rice, mashed potatoes or egg noodles—garnish with green onions, sesame seeds.