Season the chicken thighs generously with salt and pepper on both sides for maximum flavor.
Whisk the sauce by combining the molasses, soy sauce, apple cider vinegar, and ground ginger in a small bowl until smooth.
Create a vegetable bed by placing the onion wedges and whole garlic cloves into the bottom of your slow cooker.
Arrange the chicken on top of the onions, skin-side up so they baste in their own juices while cooking.
Pour the molasses mixture over the chicken, ensuring every piece is well-coated and dark.
Cover and cook on LOW for 5 to 6 hours until the meat is falling-off-the-bone tender.
Baste the chicken with the syrupy pan juices halfway through to build that rich, dark mahogany glaze.
Serve hot with the softened onions and buttery garlic cloves spooned generously over the top.