Step 1: Preheat your oven to 400°F (200°C). Prepare a large baking sheet (or two, if necessary) by lining it with parchment paper for easier cleanup.
Step 2: Wash the Brussels sprouts thoroughly under cold water. Pat them completely dry with a clean kitchen towel. Trim the tough ends of the sprouts and remove any loose or yellowed outer leaves. For smaller sprouts, halve them lengthwise. For larger ones, quarter them to ensure even cooking.
Step 3: In a large bowl, combine the prepared Brussels sprouts with olive oil, sea salt, and freshly ground black pepper. Toss well to ensure all sprouts are lightly and evenly coated.
Step 4: Spread the seasoned Brussels sprouts in a single layer on the prepared baking sheet(s). Ensure they are not overcrowded, as this will cause them to steam rather than roast and crisp up. If your sprouts don't fit in a single layer, use a second baking sheet.
Step 5: Roast for 20-25 minutes, or until the Brussels sprouts are tender-crisp and beautifully caramelized with slightly charred edges. Halfway through the cooking time (around 10-12 minutes), give the baking sheet a good shake or use tongs to flip the sprouts to ensure even browning.
Step 6: Carefully remove the hot roasted Brussels sprouts from the oven. Transfer them immediately to a serving bowl.
Step 7: Drizzle the hot sprouts generously with truffle oil. The heat will help to release the truffle's fragrant aroma. Then, sprinkle the freshly grated Parmesan cheese over the top.
Step 8: Toss gently to combine the truffle oil and Parmesan with the roasted Brussels sprouts. Serve immediately and enjoy the irresistible flavors!