1. Place chicken pieces in a large roasting pan. Keep in fridge until ready to roast.
2. Heat oil in a large frying pan. Add onions and sauté over low heat for 45 minutes, stirring occasionally. (The key here is low and slow, to achieve that sautéed yet sweet taste.) Fifteen minutes before it finishes sautéing, preheat oven to 350°F (175°C). Add the garlic, and continue sautéing for two to three minutes. Add honey, raise heat to high, and mix together for one minute. Remove from heat and add the salt and pepper.
3. Cool slightly, then blend with an immersion blender or in the food processor. Pour into a medium-sized bowl. Add the chili sauce and silan, then mix together well.
4. Spoon mixture over chicken, taking care to smother the pieces totally in sauce. Cover and bake for two hours. Lower temperature to 300°F (150°C) and uncover roasting pan. Bake for an additional 10 minutes.