01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - In a large mixing bowl, whisk together maple syrup, olive oil, balsamic vinegar, sea salt, and ground black pepper until well combined.
03 - Add the halved Brussels sprouts to the bowl and toss thoroughly to ensure even coating with the glaze.
04 - Spread Brussels sprouts cut-side down in a single layer on the prepared baking sheet.
05 - Roast for 15 minutes until slightly golden, then remove sheet from oven.
06 - Sprinkle chopped walnuts over the roasted sprouts and gently toss to incorporate.
07 - Return baking sheet to oven and continue roasting for 8 to 10 minutes, until the Brussels sprouts are tender and walnuts lightly toasted.
08 - Transfer the Brussels sprouts and walnuts to a serving bowl, garnish with fresh parsley if desired, and serve immediately.