How to Make It
In a medium saucepan, melt the butter. Add the shallot and cook over moderate heat, stirring occasionally, until softened, 2 to 3 minutes. Whisk in the flour, dry mustard, and pepper, and cook, stirring occasionally, for 1 minute. Add the cheese, ale, and Worcestershire sauce, and cook over moderately low heat, whisking, until the cheese melts, 2 to 3 minutes.
Preheat the broiler and position a rack 4 inches from the heat. Line a rimmed baking sheet with parchment paper, and arrange the toasts on top. Spoon the cheddar mixture over the toasts, and broil until bubbling and browned around the edges, about 2 minutes. Sprinkle with chives, and serve.