Separate eggs, putting the whites in a standing mixer bowl and the yolks in a separate bowl.
In a standing mixer with a whisk attachment beat the egg whites, tartar, vanilla extract and 1/4 cup of sugar. Beat on high until the mixture is at stiff peak.
In the separate bowl with the egg yolks stir in the melted butter, 3/4 cup sugar. Mix until combined.
Add the flour, cocoa powder, salt and baking powder into another bowl.
Turn the standing mixer on low, slowly pour in the egg yolk mixture.
After that is combined, slowly pour the flour mixture into the standing mixer bowl. Add the 1/8 cup of hot water. Mix until smooth.
Pour batter into a light metal cookie sheet, greased and lined with a parchment paper
Bake for 12 minutes
Remove from the oven and place a clean kitchen towel draping over the cookie sheet, trapping in steam as the cake cools.
Allow to cool for 15-20 minutes, then remove the kitchen towel
Sprinkle the 1/4 cup of powder sugar on top of the sheet cake.
Carefully roll the cake up with the parchment paper still attached to the back side of the cake. Allow the cake to sit in the rolled up state while you prepare the cream cheese filling and chocolate ganache frosting.
Cream Cheese Filling
In a standing mixer, add cream cheese and butter, mix until slightly softened
add the vanilla extract and powdered sugar, mix until combined
turn the mixer on high and whip for 2 minutes until light in color and texture.
Chocolate Ganache Frosting
In a microwave safe bowl add chocolate chips and cream, microwave for 30 seconds, stir vigorously. Repeat once. Stir until all the chocolate chips are melted.
In a standing mixer add butter, stir until softened.
Add powdered sugar and mix in until combined. It will be dry and chunky at this point.
Turn the mixer on low and slowly pour in the chocolate ganache.
Once the frosting is mixed, turn the mixer on high and whip for 2 minutes to incorporate air and lighten your frostings color and texture.
Assemble
Carefully unroll your cooled cake, spread the cream cheese filling on the top.
Re-roll your cake, this time peeling off the parchment paper on the back side.
Frost the outside of the roll in chocolate frosting. Enjoy!