3 ounces unsweetened chocolate, melted and cooled slightly
3 ounces white baking chocolate, melted and cooled slightly
1/4 cup seedless raspberry jam
1 cup semisweet chocolate chips, melted
White baking chocolate shavings
Place egg whites in a large bowl; let stand at room temperature 30 minutes. Preheat oven to 350°. Line bottoms of 2 greased matching 13x9-in. baking pans with parchment; grease papers.
In a large bowl, cream butter and sugar until light and fluffy, 5-7 minutes.
Add egg yolks, one at a time, beating well after each addition. Add vanilla. Stir in flour.
With clean beaters, beat egg whites on medium speed until stiff peaks form. Fold into batter. Transfer half of the batter to another bowl. Fold melted unsweetened chocolate into 1 bowl; spread into a prepared pan. Fold melted white chocolate into remaining batter; spread into second prepared pan.
Bake 12-16 minutes or until a toothpick inserted in center comes out clean. Cool 5 minutes. Invert onto wire racks. Remove parchment; cool completely.
Transfer chocolate layer to a baking sheet lined with a large piece of plastic wrap. Spread jam over top; place white chocolate layer over jam. Wrap securely with plastic wrap. Set a cutting board or heavy baking pan over top to flatten layers. Let stand at room temperature 3-4 hours. (Or, refrigerate overnight and return to room temperature before continuing.)
Unwrap cake; place on a cutting board. Spread top with melted chocolate chips. Top with white chocolate shavings. Let stand until set. Trim edges with a knife. Cut into 24 squares; cut squares diagonally in half.
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