Roasted Brussels Sprouts with Balsamic Onions

Preheat oven to 400°F (200°C).

In a large bowl, toss Brussels sprouts with 1 tablespoon of olive oil, salt, and pepper.

Spread Brussels sprouts in a single layer on a baking sheet.

In a large skillet or cast iron skillet, heat the remaining 2 tablespoons of olive oil over medium heat. Add sliced onions and cook, stirring occasionally, until softened and starting to caramelize, about 15-20 minutes. Reduce heat if onions are browning too quickly.

Add minced garlic to the onions and cook for another minute until fragrant.

Stir in balsamic vinegar and maple syrup (if using) to the onions. Cook for 2-3 minutes, allowing the sauce to thicken slightly.

After the Brussels sprouts have been roasting for about 15 minutes, add the caramelized onions to the baking sheet, mixing them in with the Brussels sprouts.

Return the baking sheet to the oven and roast for another 10-15 minutes, or until Brussels sprouts are tender and slightly browned.

Serve immediately.