Step 1: In a medium mixing bowl, whisk together the pineapple juice, light brown sugar, ketchup, soy sauce, minced garlic, Worcestershire sauce, salt, black pepper, onion powder, and ground ginger until the mixture is smooth and well combined.
Step 2: In a skillet, melt the unsalted butter over medium-high heat. Add the chopped yellow onion and sauté until it becomes translucent, tender, and lightly golden, about 5-7 minutes.
Step 3: Sprinkle the all-purpose flour over the sautéed onions. Cook for about 1 minute, stirring constantly, to create a roux. Gradually pour in the whisked pineapple juice mixture from Step 1, stirring continuously to prevent lumps. Bring the sauce to a boil, then reduce the heat and let it simmer for 10-15 minutes, or until it has visibly thickened.
Step 4: Arrange the boneless, skinless chicken breasts (or thighs) evenly at the bottom of your slow cooker. Pour the thickened, aromatic Hawaiian sauce directly over the chicken, ensuring it’s well coated. Cook on the LOW setting for 8 hours, or on the HIGH setting for 4 hours, until the chicken is exceptionally tender and easily pulls apart with a fork.
Step 5: Carefully remove the cooked chicken from the slow cooker and place it on a clean cutting board or a shallow dish. Using two forks, shred the chicken into bite-sized pieces. It should be so tender that it practically falls apart on its own.
Step 6: Return the shredded chicken to the slow cooker and stir it into the luscious Hawaiian sauce, making sure every piece is thoroughly coated. Serve this tropical feast immediately and prepare for rave reviews!