from How To Cook Everything Vegetarian

1 pound Brussels sprouts
1/4 cup extra virgin olive oil
5 cloves garlic, peeled, or more to taste
Salt and freshly ground black pepper
1 tablespoon balsamic vinegar

Preheat the oven to 450ºF.  Trim the hard edge of the stem from the Brussels sprouts, then cut each in half through its axis.  Put the oil in a large ovenproof skillet over medium-high heat. When it shimmers, arrange the sprouts in one layer, cut side down.  Toss in garlic and sprinkle with salt and pepper.

Cook, undisturbed, until the sprouts begin to brown, 5 to 10 minutes, then transfer to the oven.  Cook, shaking the pan occasionally, until the sprouts are quite brown and tender, about 30 minutes.

Taste and adjust the seasoning; drizzle with the balsamic vinegar, stir, and serve hot or warm.