Preheat oven to 350 degrees.
Spray a 10x15 with pam, line w parchment and spray again.
Beat the egg yolks until creamy and gradually beat in the sugar until the mixture is very thick and light in color.
Meanwhile microwave the chocolate and water until smooth and cool.
Stir the melted chocolate into the yolk mixture.
Beat the egg whites with the salt until stiff.
Fold the whites into the chocolate mixture.
Spread into the pan and bake 15-18 mins.
Cool in the pan.
Sift a layer of cocoa evenly over the cake.
Lay a piece of parchment onto a cookie sheet and carefully flip the cake onto the parchment.
Remove the original parchment it baked on.
Beat the heavy cream, with the sugarand vanilla until thick.
Spread over the chocolate roll and using the parchment paper underneath as a guide, roll the cake like a jelly roll and slide seam down onto a board or platter.
Chill several hours.
Dust with powdered sugar.