2 1/2 cups white sugar
3 tablespoons butter
1 1/2 teaspoons vanilla extract
3 cups all-purpose flour
1 teaspoon baking soda
1/2 teaspoon salt
1 cup cocoa
Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets.
Cut cookie sheets into 3 inch squares. Spread 1 teaspoon of the sugar mixture evenly into each square. Layer butter filling with remaining sugar mixture, top with cocoa and 1/2 teaspoon vanilla. Brush or spray sides of paper pan with egg white. Place 1/2 teaspoon filling in center of each cookie.
Bake for 8 to 10 minutes in preheated oven, or until edges begin to crack. Remove from cookie sheets. Cool slightly. Serve warm.