4 oz extra-sharp Cheddar cheese, finely shredded (about 1 cup)
¼ cup unsalted butter, softened
¼ cup mayo
1 ½ tsp cornstarch
1 tsp hot sauce (such as Tabasco)
1 tsp Worcestershire sauce
½ tsp kosher salt
¼ tsp dry mustard
¼ tsp paprika
3 large egg whites, at room temperature
⅛ tsp cream of tartar
5 (1 ½-oz) thick-cut, firm white sandwich bread slices
Method
Stir together cheese, butter, mayo, cornstarch, hot sauce, Worcestershire, salt, mustard, and paprika in a large bowl until creamy and combined.
Beat egg whites and cream of tartar in a medium bowl with an electric mixer on high speed until stiff peaks form (1 minutes, 30 seconds to 2 minutes). Gently fold egg white mixture into cheese mixture in 4 additions, being careful not to overmix to avoid deflating egg whites; mixture should remain light and airy. Refrigerate, uncovered, until ready to use.
Trim crusts from bread slices. Cut slices in half crosswise; cut each half into thirds to make a total of 30 pieces.
Spread cheese mixture evenly over tops and sides of bread pieces. Arrange on a baking sheet coated with cooking spray. Chill, uncovered, until firm, 30 minutes to 1 hour. (To store in the freezer, freeze on a baking sheet until firme, 30 minutes to 1 hour. Then transfer to a heavy-duty ziplock plastic freezer bag, and freeze for up to 3 months. Do not thaw before baking.)
While bread pieces chill, preheat oven to 375 F. Bake chilled bread pieces until golden brown and slightly puffed, 10 to 12 minutes. Serve warm.
