Preheat the oven to 400 degrees F. Grease an 11x17x1 inch jelly roll pan. Line the pan with parchment paper and generously grease with butter. Set aside.
In a standing mixer, whisk the egg yolks and the sugar until pale and fluffy.
In a small pan, combine the chocolate, water and espresso and melt over low heat. Stir into the yolk mixture.
In a standing mixer and in a very clean bowl, whisk the egg whites until firm peaks form. Stir a small amount of the white into the yolk mixture to loosen and then fold in the remaining whites. Spread the batter evenly in the pan and bake for 12-15 minutes or until firm to the touch.
Let the cake cool completely before inverting it onto another sheet of parchment paper. Carefully peel away the paper it was baked on. Spread the whipped cream all over the cake. Starting at one of the smaller ends, gently role the cake into itself. Trim the ends a little and dust with powdered sugar.
The cake may be made the day before and stored in the refrigerator. Let it come to room temperature before serving.
Recipe by Culinary Thymes at https://www.culinarythymes.com/valentines-dessert-chocolate-roulade/