Barbecued Chicken In A Bag

• 2,700 ml broiler fryers up (cut)
• 60 ml water
• 45 ml ketchup
• 40 gr unbleached all-purpose flour
• 40 gr brown sugar packed
• 30 ml cider vinegar
• 30 ml worcestershire sauce
• 28 gr butter
• 16 ml lemon juice
• 10 ml dry mustard