Step 1: Season the Chicken : Pat chicken thighs dry with paper towels. Season generously with salt, pepper, smoked paprika, and garlic powder on both sides.
Step 2: Sear the Chicken : Heat olive oil in a large oven-safe or cast-iron skillet over medium-high heat. Place chicken skin-side down and sear for 4–5 minutes until golden and crisp. Flip and cook another 3 minutes. Remove chicken from skillet and set aside.
Step 3: Cook the Vegetables : In the same skillet, add Brussels sprouts and sweet potatoes. Sauté for 7–8 minutes, stirring occasionally, until they begin to brown and soften slightly.
Step 4: Add Aromatics and Apples : Stir in sliced red onion and apple. Cook another 2–3 minutes until the apples just begin to soften and the onions become fragrant.
Step 5: Make the Glaze : In a small bowl, whisk together maple syrup, Dijon mustard, chicken broth, apple cider vinegar (if using), and thyme. Pour this mixture into the skillet with the veggies. Stir gently to coat.
Step 6: Finish Cooking : Nestle the chicken thighs back into the skillet, skin side up. Reduce heat to medium-low. Cover and let everything simmer for 15–18 minutes, or until the chicken is cooked through (internal temperature reaches 165°F / 74°C) and the veggies are tender.