Prepare Chicken & Sauté Aromatics: In a large skillet, heat olive oil over medium-high heat. Add chicken pieces and cook until lightly browned on all sides, about 3-5 minutes. This step is optional but adds depth of flavor. Transfer chicken to the slow cooker. Add chopped onion to the same skillet and sauté until softened, about 5 minutes. Stir in minced garlic and cook for another minute until fragrant. Transfer onion and garlic to the slow cooker.
Combine Ingredients in Slow Cooker: Add the rinsed long-grain white rice, chicken broth, dried thyme, paprika, salt, and pepper to the slow cooker with the chicken and aromatics. Stir gently to combine, ensuring the rice is submerged in the liquid. If you prefer a creamier consistency, you can omit the browning step and add all ingredients directly, though browning does enhance the flavor profile.
Cook on Low or High: Cover the slow cooker and cook on low for 3-4 hours or on high for 1.5-2 hours. The goal is for the chicken to be cooked through and the rice to be nearly tender. Cooking times can vary based on your slow cooker model, so monitor accordingly. Avoid lifting the lid too often, as this releases heat and can significantly extend the overall cooking time.
Add Vegetables & Finish Cooking: Once the chicken is cooked and rice is almost tender, stir in the frozen mixed vegetables. Cover and continue cooking for another 30-60 minutes on high, or until the vegetables are tender-crisp and the rice is fully cooked and has absorbed most of the liquid. If you desire a thicker sauce, whisk together cornstarch and cold water to create a slurry, then stir it into the slow cooker. Cook for an additional 15-20 minutes until thickened.
Serve & Garnish: Carefully stir the Slow Cooker Chicken & Rice to combine all ingredients. Taste and adjust seasonings as needed. Garnish with fresh chopped parsley before serving hot. This hearty and flavorful meal is perfect on its own or paired with a simple green salad for a complete and satisfying dinner.