Preheat oven to 350 degrees F. Line 18 x 13-inch baking sheet pan with parchment paper and lightly mist with non-stick spray.
Sift together flour and cocoa. Set aside.
Separate 4 eggs, placing whites in a medium bowl and yolks in a large bowl. Beat egg whites until foamy. Slowly add 3/4 cup sugar and beat until mixture is shiny and thickened. Set aside.
Beat yolks with remaining 1/2 cup sugar until mixture is thick and pale in color. Add remaining whole eggs and beat until well combined. Add white eggs to yolk mixture and fold to combine.
Add dry flour mixture to mixing bowl and fold to combine. Spread cake batter in an even layer on prepared baking sheet. Bake for 15 minutes until toothpick inserted in cake comes out clean. While cake is still warm, brush cake with bourbon. Let cake cool in pan.