How to Make It
Preheat oven to 350°.
Process crackers in a food processor until fine crumbs form; transfer to a large bowl. Add 3 tablespoons sugar, butter, 1/4 teaspoon salt, 1 egg white, and whole egg, stirring to combine.
Press crumb mixture into bottom of a 13- x 18-inch jelly-roll pan coated with cooking spray. Bake at 350° for 8 minutes or until crust is set. Remove from oven; sprinkle chocolate in an even layer over hot crust, spreading evenly as the chocolate melts. Cool completely in pan on a wire rack.
Preheat broiler to high.
Place remaining 4 egg whites in a large bowl. Add vanilla, cream of tartar, and remaining 1/8 teaspoon salt; beat with a mixer at high speed until soft peaks form. Combine remaining 1 cup sugar and 1/3 cup water in a saucepan; bring to a boil. Cook, without stirring, until a candy thermometer registers 250°. Gradually pour hot sugar syrup in a thin stream over egg whites, beating at medium-low speed, then at high speed until stiff peaks form. Spread meringue over cooled chocolate-graham crust. Place pan on middle rack of oven; broil 1 1/2 minutes or until meringue topping is toasted and golden brown. Let stand 5 minutes. Cut into 30 squares. Serve warm or at room temperature.