Braised Brussels Sprouts with Balsamic and Grapes

Melt 1 tablespoon unsalted butter in a nonstick skillet over medium heat; add 1 pound trimmed and halved medium Brussels sprouts to pan, cut side down. Cook 3 minutes, without stirring. Stir in 1 cup seedless red grapes and 1 tablespoon minced garlic; cook 1 minute. Sprinkle with ⅜ teaspoon kosher salt and ¼ teaspoon black pepper. Add ¼ cup unsalted chicken stock; cover partially, and cook 3 minutes. Stir in 1 tablespoon balsamic vinegar and 1 tablespoon unsalted chicken stock; simmer 1 minute.