01 - Combine chicken thighs, diced onion, sliced carrots, celery, minced garlic, chicken broth, thyme, parsley, bay leaf, salt, and black pepper in the slow cooker. Stir thoroughly to distribute ingredients evenly.
02 - Cover and cook on low setting for 5 hours until chicken is tender and fully cooked through.
03 - Remove cooked chicken from the slow cooker and shred using two forks. Return shredded chicken back to the slow cooker.
04 - Melt 2 tablespoons butter in a small saucepan over medium heat. Whisk in 3 tablespoons flour and cook for 1 minute. Gradually whisk in 1 cup milk and 1/4 cup cream until smooth and slightly thickened. Pour mixture into the slow cooker and stir well to combine.
05 - Combine flour, baking powder, and salt in a mixing bowl. Cut in cold butter until mixture resembles coarse crumbs. Stir in milk and parsley until just combined; avoid overmixing to ensure tender dumplings.
06 - Drop spoonfuls of dumpling batter (approximately 2 tablespoons each) onto the surface of the stew. Cover and cook on high for 1 hour until dumplings are cooked through and fluffy.
07 - Remove and discard bay leaf. Ladle hot stew into bowls and serve immediately.