Rinse the long-grain brown rice under cold water several times to remove excess starch. Boil 2 cups of low-sodium chicken broth in a medium pot, add the rice, and cook for 10 minutes. Drain excess liquid and set aside.

Coat the slow cooker with nonstick spray. Add the cooked rice, diced carrots, shallot, and Dijon mustard to the slow cooker. Stir well and layer the boneless chicken breasts on top.

Season the chicken with garlic powder, dried thyme, kosher salt, and ground black pepper. Pour the remaining 2.5 cups of chicken broth over the mixture in the slow cooker.

Cover and cook on high for 1.5 to 2 hours, checking that the chicken reaches an internal temperature of 165°F.

Remove the chicken, stir the rice and vegetable mixture, and cook uncovered on high for an additional 1 to 1.5 hours. Add more broth if the mixture dries out.

Stir in frozen peas and Greek yogurt, then mix chopped chicken back into the cooker with ¼ cup of cheddar cheese. Top with the remaining cheese and cover until melted.

Serve warm, garnished with chopped parsley, and enjoy!