Crock Pot Chipotle Pulled Chicken

Name: Crock Pot Chipotle Pulled Chicken
Ingredients: 2 cups ketchup; 1 medium onion, finely chopped; 1/4 cup Worcestershire sauce; 3 tablespoons reduced-sodium soy sauce; 2 tablespoons brown sugar; 2 tablespoons cider vinegar; 1 tablespoon yellow or spicy mustard; 1 tablespoon molasses; 3 garlic cloves, minced; 2 teaspoons dried oregano; 1 teaspoon ground cumin; 1 teaspoon paprika; 1/4 teaspoon salt; 1/4 teaspoon crushed red pepper flakes; 1-2 chipotle peppers, chopped plus 2 teaspoons adobo sauce; 4 boneless, skinless chicken breasts