Place chicken wings in slow cooker crock.

In a medium saucepan over medium-high, melt butter. Add onion and garlic. Cook until onions are translucent, about 2 minutes. Add syrup, bourbon, ketchup, soy sauce, salt and black pepper. Cook until the sauce has reached a boil and is slightly thickened, 8 to 10 minutes

Reserve ¾ cup sauce. Pour remaining sauce over wings. Turn to coat with sauce mixture.

Cover slow cooker and cook on HIGH for 1 1/2 to 2 hours or LOW for 3 to 4 hours. Wings will not be completely cooked.

Heat broiler on HIGH. Turning and brushing with wings with reserved sauce, broil 10 to 15 minutes or until wings are browned and crispy.