Line two half sheet pans with Gefen Parchment Paper. Set aside. Preheat oven to 350°F.

Sift together potato starch, cocoa and salt. Set aside. Place the room temperature egg yolks in a large mixing bowl. Using an electric mixer fitted with a whisk attachment, beat the egg yolks and half the sugar until the mixture is light yellow and tripled in volume, about three minutes, scraping down the sides of the bowl periodically. Add in the water and vanilla. Beat on high for another minute until the water and vanilla are incorporated.

Using a large rubber spatula, fold in half the sifted dry ingredients into the yolk mixture.

Combine room temperature egg whites with the vinegar in a large mixing bowl. Using an electric mixer fitted with a clean, dry, whisk attachment, whip egg whites on high speed until very foamy and increased in volume. Gradually add remaining sugar in a steady stream. Whip just until stiff peaks form. Do not overbeat.

Fold the egg whites into the yolk mixture in three additions. Sift remaining dry ingredients into the egg mixture in two additions, scraping the sides and bottom of the bowl and being very careful not to deflate the batter.

Divide the batter between the two pans. Smooth with a spatula. Bake for 15 minutes. Rotate pans and bake an additional seven minutes, until cakes spring back when touched. Remove from oven and place on racks to cool.

In a medium saucepan, bring cream to a boil. Remove from heat. Add chocolate chips to the cream, but do not mix. Let mixture rest for two to three minutes. Mix until smooth.

Allow to cool for 30 minutes before glazing cake.

Place cold water in a small bowl. Sprinkle gelatin over the water and immediately mix with a whisk to remove any lumps. Set aside for at least five minutes, whisking periodically to remove any additional lumps.

Fill a pot one third of the way with hot water. Bring to a boil, then reduce heat to medium-low to simmer. Place egg whites and sugar in a clean, dry bowl of an electric mixer. Set the bowl over the simmering water. Whisk continuously until the mixture is hot to the touch, when you feel the egg white mixture it doesn’t feel gritty and all the sugar is dissolved. 

Fold the melted chocolate into the beaten egg whites. Set aside.

In a separate mixing bowl, whip the cream until it holds a peak. Fold the cream into the whites, being very careful not to deflate the whites.

Remove the bowl from the heat, add in the gelatin mixture, and beat on high speed until the egg whites cool and form very stiff peaks, approximately five to seven minutes depending upon your mixer.

Using a very sharp, serrated knife, loosen cakes from sides of pans. Invert each cake onto a piece of parchment paper the size of the pan. Remove parchment liner from the cake. Using a ruler to ensure even sections, divide each of the cakes into 3 sections lengthwise. You will have six cake sections, each approximately four inches wide. Trim ends if desired.

Place one of the cake sections, bottom side up, on a long cake plate or cake board. Cover with a thin layer of mousse. Smooth the mousse with an offset spatula.

Repeat step 2, layering remaining cake and mousse, finishing with a cake layer, being careful to keep the mousse within an eighth inch of the edges of the cake.

Cover the entire cake with a very thin layer of the prepared ganache. Smooth with an offset spatula. This layer of ganache is used to set the cake.

Refrigerate cake for 30 minutes until ganache is set.

Remove cake from refrigerator and cover with an additional layer of ganache. Decorate with remaining ganache.

Refrigerate at least an hour before serving. Serve with chocolate drizzle and fresh fruit.