• Preheat the oven to 170 C / 340 F 
• Grease and line with parchment paper a 15 x 10 sheet pan. Make sure the parchments covered the sides of the pan as well. 
• Combine flour with cocoa powder, half the salt, baking powder - set aside. 
• Separate the eggs - white in a clean grease free bowl and yolks in a separate bowl 
• Whip the egg whites with half the sugar, remaining salt, and cream of tartar - set aside
• Whip the egg yolks with the remaining sugar for two minutes. Add the vanilla extract, cream, and sift in the flour mixture
• Fold the egg whites into the yolk mixture. Finally, fold in melted butter.
• Pour into the prepared baking tray. Bake for about 12 to 14 minutes until the top is springy and set. 

When Baked

• Remove it out from the oven and instantly transfer to a cooling rack
  (I simply drag the parchment from the sheet pan to the cooling rack) 
• Dust the top of the cake with cocoa powder or powdered sugar
  (this will prevent the cake from sticking to the parchment paper.
• Use another pan and parchment paper to flip the cake over. 
• Now, carefully peel the top parchment paper - the one that cake was baked in. 
• Place a slightly damp kitchen towel or cheesecloth on the top of the cake. Roll the cake into a jelly roll. This prevents it from sticking when you unroll later.
• I roll from the long side.  But you can roll from the short side for more spirals. 
• Let cool in this rolled position until cooled completely (not in the fridge) 

Decorate

• Whip the cream with powdered sugar until still peaks.
• When cooled unroll the cake. Place it on a firm worktop or sheet pan. 
• Trim both the edges at an angle so they are tapering (this helps the finished cake rest on itself properly (optional) 
• Brush the cake with simple syrup. 
• Followed by the whipped cream
• Firmly roll the cake back into a jelly roll. 
• Place in the fridge for at least two hours wrapped. This will ensure you have nice firm pretty slices. 
• Dust with powdered sugar, if desired.
• Enjoy!