Step 1
Place white chocolate chips and 3/4 cup heavy cream for white chocolate filling in a medium microwave-safe bowl. Microwave on 50% power until chocolate is completely melted and cream is fully incorporated about 2 minutes stopping to stir every 30 seconds. Set aside and allow to cool to room temperature 10 to 20 minutes. Place into the refrigerator until completely chilled at least 4 hours to overnight.
Step 2
Meanwhile place dark chocolate chips and 3/4 cup heavy cream for dark chocolate filling into another medium microwave-safe bowl. Microwave on 50% power until chocolate is melted and cream is fully incorporated about 2 minutes stopping to stir every 30 seconds. Set aside and allow to cool to room temperature 10 to 20 minutes. Place into the refrigerator until completely chilled at least 4 hours to overnight.
Step 3
Preheat the oven to 350 degrees F (175 degrees C). Line a 12x17-inch baking sheet with parchment paper. Grease the pan and parchment.
Step 4
Combine egg yolks and brown sugar in a large bowl. Beat at medium-high speed until mixture is light and creamy about 2 minutes. Mix in butter coffee and vanilla extract.
Step 5
Sift flour 1/3 cup cocoa baking powder baking soda and salt together in a small bowl. Add to egg yolk mixture; mix until just combined.
Step 6
Beat egg whites in a separate clean dry large bowl with clean dry beaters on high speed until soft peaks form. Gradually add sugar 1 tablespoon at a time beating constantly. Continue to beat until mixture is glossy and stiff peaks form. Fold 1/3 of the egg white mixture gently into the yolk mixture until just combined. Fold in remaining egg whites gently until no streaks of egg white remain. Do not overmix.
Step 7
Pour batter into the prepared pan and gently spread evenly.
Step 8
Bake in the preheated oven until cake springs back lightly when touched about 10 minutes. Do not overbake.
Step 9
While cake is baking prepare a piece of parchment paper that is slightly larger than the baking pan. Sprinkle lightly with remaining cocoa powder.
Step 9
Remove cake from the oven and run a knife around the edges of the pan to loosen the cake. Invert the cake quickly and carefully as pan will be hot onto the cocoa-sprinkled parchment paper. Remove the piece of parchment the cake baked on and discard. Working quickly roll the cake and cocoa-sprinkled paper up together starting from the narrow end. Set the cake seam-side down on a wire rack to cool completely 1 to 2 hours.