In a large dutch oven, cook the bacon until crisp. Set the bacon aside to cool, then pack away and save to garnish the finished dish.
Pour out all but 2 tablespoons of the bacon grease from the pan. Season the chicken with salt and pepper. Heat the bacon grease over medium-high heat and brown the chicken on both sides, 4-5 minutes per side. You will probably have to do this in 2 batches. Transfer browned chicken to the slow-cooker.
Add the onions, 1 teaspoon brown sugar, and water to the dutch oven. Scrap the bottom of the pan to get up any brown bits (the flavor!) and cook the onions for 4-5 minutes until soft. Add the garlic and cook for 30 seconds. Pour the onion mixture into the slow-cooker.
Add the thyme, chicken stock, soy sauce, bay leaves, and remaining 1 tablespoon brown sugar to the slow-cooker. Cook on low for 6-8 hours.
When ready to serve, transfer the chicken to a platter. Discard bay leaves and pour liquid through a mesh strainer into a saucepan, reserving the solids. Remove any pieces of chicken or cartilage from the solids. Transfer solids to a food processor or blender with 1 cup liquid and blend until smooth. Stir the blended mixture back into remaining liquid in the saucepan.
Heat the liquid over medium heat. In a small dish, mix together the arrowroot powder (or cornstarch) and water. Pour the mixture into the liquid while whisking quickly. Add the cider vinegar and continue to cook until the mixture is thick and bubbly, about 5 minutes. Pour the gravy over the chicken and top with the fresh parsley and reserved crumbled bacon. Serve and enjoy!