Chop the chocolate into small pieces. (The smaller, the faster it will melt.) Melt it over a double boiler until smooth, stirring occasionally.

Separate the egg yolks from the whites and chill the egg whites until needed.

In a medium bowl, beat the egg yolks and sugar until pale and smooth with a hand-mixer, for about 2 minutes. 

Mix the coffee powder with the espresso and rum until the coffee granules have dissolved and add into the egg mixture. Then stir in the sifted cocoa.

Then add in the warm chocolate and stir until smooth.

In a clean and grease-free bowl, beat the chilled egg whites along with a pinch of salt until stiff glossy peaks form.

In a separate bowl, beat the whipped cream until stiff peaks form and set aside.

Gently fold the egg whites into the chocolate mixture with a spatula until smooth. Then fold in the whipped cream.

Pour into desired glasses and chill for at least 6 hours or overnight. Optional: Sprinkle with cocoa powder before serving.