Quick and Easy BBQ Chicken Sandwich

Ingredients

• 1/2 cup chopped onion
• 1/2 cup diced celery
• 1 garlic clove, minced
• 1 tablespoon butter
• 1/2 cup salsa
• 1/2 cup ketchup
• 2 tablespoons brown sugar
• 2 tablespoons cider vinegar
• 1 tablespoon Worcestershire sauce
• 1/2 teaspoon chili powder
• 1/4 teaspoon salt
• 1/8 teaspoon pepper
• 2 cups shredded cooked chicken
• 6 hamburger buns, split and toasted
• Dill pickle slices, optional