Brussels Sprouts Gratin

Boil Brussels sprouts in large pot of boiling salted water until crisp-tender, 5-8 minutes Drain and run under cold water to cool Spread in single layer, on paper towel-lined baking sheet, dry completely Cook garlic in butter in large saucepan over medium heat until fragrant, 1 minute Sprinkle with flour, cook; whisking, 1minute Slowly whisk in half-and-half Simmer, whisking often, until thickened, 6-7 minutes Remove from heat and whisk in 6 ounces gruyere, fold in Brussels sprouts Season with salt and pepper Transfer to a buttered 3 quart baking dish Top with remaining gruyere Bake @375F until bubbly and top is golden brown, 25-30 minutes Let sit 5 minutes before serving