Beer Cheese Fondue

Bring the beer to a boil over medium-high heat in a fondue pot or a medium heavy saucepan. Reduce the heat to medium-low so the beer is gently simmering. Toss the Gruyère with the cornstarch in a medium bowl. Add the cheese mixture to the beer one large handful at a time, stirring the cheese in a figure-eight pattern until completely melted before adding more. Stir in the mustard, Worcestershire sauce, and paprika, and season with salt. Serve immediately. The fondue can be refrigerated, covered, for up to 2 days and then rewarmed over medium-low heat, stirring in a figure-eight pattern, until the cheese is melted and hot.