In a large mixing bowl, combine the halved Brussels sprouts with olive oil, salt, pepper, and garlic powder. Toss until the sprouts are evenly coated.
In a large skillet over medium heat, cook the diced bacon until crispy, about 5-7 minutes. Use a slotted spoon to transfer cooked bacon to a paper towel-lined plate, leaving the bacon fat in the skillet.
In the same skillet with the bacon fat, add the coated Brussels sprouts. Sauté for about 5 minutes until they begin to caramelize.
Add the crispy bacon back into the skillet with the Brussels sprouts. Drizzle the maple syrup and apple cider vinegar over the mixture. Stir well to combine, ensuring each sprout is coated.
Transfer the Brussels sprouts and bacon mixture to a baking dish. Roast in the preheated oven for about 15-20 minutes, or until the sprouts are tender and caramelized.
Once out of the oven, sprinkle with freshly grated Parmesan cheese (if using) and garnish with chopped parsley. Serve hot as a delightful side dish or snack!