Instructions:
- Chop the onion, carrots, and celery into rough, uniform pieces.
- Place the chopped vegetables at the bottom of the slow cooker insert.
- Pat the chicken pieces dry. Season generously on all sides with salt, pepper, garlic powder, thyme, and rosemary.
- Place the seasoned chicken on top of the vegetables. Pour the chicken broth evenly over everything.
- Cover the slow cooker. Cook on LOW for 6 to 8 hours or on HIGH for 3 to 4 hours, until the chicken is easily shreddable with a fork.
- Carefully remove the cooked chicken to a large bowl. Use two forks to shred the meat coarsely.
- Pour the remaining cooking liquid through a fine-mesh sieve into a heat-safe bowl. Discard the cooked vegetables.
- In a small saucepan over medium heat, melt the 2 tablespoons of butter. Whisk in the flour until a smooth paste forms, cooking for 1 minute.
- Gradually whisk about 3 cups of the reserved cooking liquid into the flour/butter paste, ensuring no lumps form. Bring to a gentle simmer, whisking frequently, until the gravy thickens.
- Return the shredded chicken to the slow cooker. Pour the thickened gravy over the chicken and stir gently to coat.
- Keep warm on the 'Keep Warm' setting for 15 minutes to allow flavours to meld.
- Garnish generously with fresh parsley before serving piping hot over mashed potatoes.