Browning butter brings out a mellow nuttiness that complements the strong flavor of the sprouts, a perfect side dish for Thanksgiving or any other time of year.
Position a rack in bottom third of the oven and preheat to 450 degrees.
Place the butter on a large rimmed baking sheet and roast until the butter is melted, browned, and fragrant, 4-5 minutes. Remove the baking sheet from the oven. Toss the Brussels sprouts and hazelnuts with the browned butter and season with the salt and pepper, to taste.
Return to the oven and roast for 7 minutes. Sprinkle with the water, toss, and continue roasting until the sprouts are tender and browned lightly, 7-9 more minutes.