Step 1: In a large, oven-safe skillet (preferably cast iron), cook the diced bacon over medium heat until crispy. Remove the bacon with a slotted spoon, reserving 1-2 tablespoons of grease in the skillet. Crumble the bacon and set aside.
Step 2: Add the diced onion to the skillet and sauté for 4-5 minutes until softened. Stir in the minced garlic and cook for another 30 seconds until fragrant. Remove the onion and garlic from the skillet and set aside.
Step 3: Add the chicken pieces to the skillet. Season generously with half of the salt and pepper. Cook, stirring occasionally, until browned on all sides and cooked through, about 6-8 minutes. Remove the chicken from the skillet and set aside with the onion and garlic.
Step 4: If needed, add a tablespoon of olive oil to the skillet. Add the diced sweet potatoes and halved Brussels sprouts. Season with cinnamon, nutmeg, and the remaining salt and pepper. Sauté for 5-7 minutes, stirring occasionally, until the vegetables begin to soften and lightly brown.
Step 5: Stir in the diced apple and chicken broth. Bring to a simmer, then cover the skillet and cook for 10-12 minutes, or until the sweet potatoes are tender. Stir occasionally and add a splash more broth if the pan becomes too dry.
Step 6: Return the cooked chicken, sautéed onion, and garlic to the skillet. Stir in the chopped walnuts, dried cranberries, and fresh thyme. Cook for another 2-3 minutes, stirring gently, to warm everything through and allow the flavors to meld.
Step 7: Taste and adjust seasoning as needed. Serve hot, topped with the crumbled crispy bacon.