How to Make It
Preheat oven to 425°F. Lightly coat 6 (8-ounce) cocottes or ramekins with cooking spray; set aside. Bring 4 quarts water to a boil in a large pot over high. Add 1/3 cup salt; let water return to a boil. Add broccoli; cook, stirring occasionally, until just tender, about 3 minutes. Drain. Transfer broccoli to a large bowl filled with ice water; let stand 5 minutes. Drain. Arrange broccoli in a single layer on a baking sheet lined with paper towels; pat dry. Transfer broccoli to a large bowl; set aside.
Melt 1/2 cup butter in a large saucepan over medium. Add onion; cook, stirring occasionally, until softened, about 8 minutes. Gradually whisk in flour; cook, whisking constantly, until flour is completely incorporated and lightly browned, about 2 minutes. Gradually whisk in beer and half-and-half; cook, whisking constantly, until sauce thickens and begins to bubble, 3 to 4 minutes. Gradually whisk in cheese, Worcestershire, dry mustard, pepper, and 2 teaspoons salt until smooth.
Pour cheese sauce over broccoli; stir to combine. Season with salt to taste. Spoon mixture evenly into prepared cocottes, and arrange on a rimmed baking sheet.
Microwave remaining 2 tablespoons butter in a medium-size microwavable bowl on HIGH until melted, 30 seconds to 1 minute. Add bread pieces and remaining 1/4 teaspoon salt; toss to coat. Sprinkle mixture evenly over broccoli mixture in cocottes. Bake, uncovered, in preheated oven until bread is golden brown and cheese is bubbly, 16 to 20 minutes.
Recipe may be prepared in a 9-inch square baking dish.