Prepare slaw: Stir together mayonnaise, lemon juice, and granulated sugar until smooth. Stir in coleslaw mix and parsley. Add salt and pepper to taste. Prepare sauce: Stir together ketchup and next 7 ingredients in a medium saucepan. Cook over medium-low heat, stirring occasionally, 15 minutes or until bubbly. Stir together 1/2 cup barbecue sauce and chicken in a bowl. Spoon mixture over Texas toast slices. Serve with slaw and remaining barbecue sauce.