Grilled BBQ Chicken Sandwiches

Name: Grilled BBQ Chicken Sandwiches
Ingredients: 2 cups ketchup; 1/2 cup apple cider vinegar; 1/2 cup dark brown sugar; 2 tablespoons Worcestershire sauce; 1 teaspoon freshly ground black pepper; 1 teaspoon garlic powder; 1 teaspoon dry mustard; 1 teaspoon onion powder; 1 teaspoon hot sauce; Olive oil, for lightly coating the chicken; 4 chicken cutlets, pounded to 1/2 inch thick; Kosher salt and freshly ground black pepper; 8 potato buns; Mayonnaise, for spreading; 1 medium red onion, sliced; 16 bread-and-butter pickle slices