• Preheat oven to 350 degrees. Line a 12 x 16 jelly roll pan (baking sheet with a rim) with parchment paper and dust it with powdered sugar.
• Sift the flour, cocoa powder and baking powder together into a small bowl, set aside.
• Separate the eggs by adding the yolks to a large mixing bowl and the whites to another separate large mixing bowl.
• To the bowl with yolks, add in ½ cup of sugar, salt, corn syrup, vanilla and water. Set this bowl inside a slightly larger bowl filled with warm tap water. Beat the yolks on high speed until they become pale yellow, thick and foamy. Remove the bowl of yolks from the water.
• Microwave the oil until warm. Add the oil to the small bowl of sifted, dry ingredients and whisk to combine. Add this chocolate and oil mixture to the egg yolk mixture and whisk gently until smooth.
• In the large bowl with egg whites, beat on high speed until they become frothy, thick and start to hold their shape. Slowly add the sugar a little at a time, mixing well in between. Continue to beat on high until stiff peaks form. (You should be able to dip a finger into the mixture and when you remove it the mixture should be able to stand with a peak).
• Add the meringue mixture to the egg yolk mixture and gently fold this together with a silicone spatula until the batter is JUST evenly incorporated. (We want our cake to be soft and fluffy, so we don’t want to deflate the air out of our meringue while combining).
• Pour the batter into the prepared jelly roll pan and tap it gently on the counter a few times to make sure it spreads evenly.
• Bake for 15-20 minutes or until a toothpick inserted in the center of the cake comes out clean. Do not overbake or it will dry out and crack.
• While baking, grab a clean dish towel, slightly dampen and lay it flat on the counter and sprinkle generously with powdered sugar.
• Remove from the oven and immediately flip the pan upside down onto the sugared towel. The cake should easily release from the pan. Remove the pan and the parchment paper. Use the towel to gently roll the cake into a spiral and allow it to cool in this position. Once cool, you can unroll the towel for the filling.

Marshmallow Buttercream

• Add the powdered sugar, vanilla and butter to a large mixing bowl. Beat with a stand or hand mixer until smooth. Add the marshmallow fluff and mix again until completely combined.
• Gently unroll the cake, evenly spread the filling over the top and gently roll back up. Set the cake seam side down on a wire rack placed over a baking sheet.

Dark Chocolate Ganache

• Microwave the heavy cream until it just starts to bubble. Add the broken chocolate pieces to the cream. Allow the chocolate to sit for a minute or so, then stir to combine. Use an offset spatula to ensure all sides are covered. Allow the ganache to set and then you’re ready to serve!