Preheat oven to 325º. Grease 15x10x1” jelly roll pan, Lined with waxed paper. Grease the paper.
Sift the flour, cocoa, and salt into a small bowl; set aside. Beat the egg yolks and 1/3 cup sugar in a large mixing bowl with an electric mixer until they are thick andpale, about 2 min. On low speed, gradually mix in water, 2 tablespoons crème de cacao and vanilla until smooth.
Beat the egg whites with an electric mixer on high speed until soft mounds form. Slowly add the remaining ½ cup sugar, beating until the whites are stiff, and shiny peaks form. Stir a dollop of whites into the egg-yolk mixture to lighten it. Pour the cocoa mixture and the remaining whites over the yolks and fold them together. Pour the batter into the prepared pan, spreading evenly. Bake 10-16 min or until a pick inserted in center comes out clean.Cool the cake until lukewarm and brush the top with 2 tablespoon crème de cacao. Cool to room temperature.
White Chocolate Buttercream: Melt the chocolate in the cream in a double boiler over simmering water, stirring until smooth; cool slightly. Cream the butter with an electric mixer until light and creamy. Beat in the egg yolks, one at a time, mixing until light and fluffy. Mix in the chocolate and crème de cacao on low speed. If the buttercream is too thin, refrigerate until thickened, 15-30 min.
Go around cake with the tip of a sharp knife. Remove the cake from the pan using the paper as handles and invert it on a cutting board. Remove the paper. Trim the edges of the cake. Cut it crosswise into 3 equal parts, approx 4-5” wide. Place one slice on a piece of foil and spread with ½ of the buttercream frosting. Top with the second layer and spread with remaining buttercream. Top with the third layer. Refrigerate until firm.
Make the White and Dark chocolate dough (recipes follow).
Roll 1 recipe of White Chocolate between 2 sheets of waxed paper until ¼” thick. Place over ½ of cake, trimming the edges even with the bottom of the cake. Fold in the corners like wrapping paper. Repeat with the second recipe of White Chocolate dough, meeting in the middle and covering the second half of the cake. Roll out the Dark Chocolate dough between 2 sheets of waxed paper until about ¼” thick and cut into bands or strips about 1” wide. Wrap one band around the width of cake, covering the seam where the pieces of white chocolate meet. Wrap another band around the length of the cake. Top the dark chocolate with thinner strips of white chocolate dough, if desired, TO make bows by forming loops of dark and white chocolate dough, press gently into center of cake, Refrigerate until serving or overnight. To serve cut into thin strips.
Dark Chocolate Dough: Melt the chocolate and syrup in the top of a double boiler over simmering water, stirring with a rubber spatula, until mixture is smooth. Pour into a small bowl and cover with plastic wrap directly on dough. Let the mixture stand in a cool place for 4-8 hours, or until it forms a soft, shiny, pliable dough.
Repeat previous instructions using the ingredients for the White Chocolate Syrup