Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper to prevent sticking.
Wash and trim the ends of the Brussels sprouts, then slice them in half lengthwise to create more surface area for browning.
Cut the chicken breast into uniform one-inch cubes to ensure they cook at the same rate as the vegetables.
In a large mixing bowl, combine the halved sprouts and chicken pieces with the extra virgin olive oil, sea salt, black pepper, and garlic powder.
Toss the mixture thoroughly until every piece is well-coated in the oil and seasonings.
Spread the chicken and sprouts onto the prepared baking sheet in a single layer, making sure not to overcrowd the pan so they roast rather than steam.
Place the tray in the oven and roast for 20 to 25 minutes, tossing the ingredients halfway through, until the chicken is cooked through and the sprouts are golden brown.
While the tray is roasting, whisk together the balsamic vinegar and maple syrup in a small bowl until smooth.
Remove the pan from the oven, drizzle the balsamic glaze over the hot ingredients, and sprinkle with chopped pecans before serving immediately.