In a bowl, beat the 5 egg whites with 1/2 of the powdered sugar, then add flour and beat until the mixture becomes homogenized. Add the pre-melted (but not hot) butter in the bowl and mix well.
Melt the crumbled or couverture chocolate in a water bath, let it cool, and while it is still liquid, mix it with the rest of the mixture, along with 2 teaspoons of Mocha coffee.
Beat the 5 egg whites with the rest of the powdered sugar into hard snow. Mix the brown mixture with the egg white one while stirring carefully..
Grease the baking trays and sprinkle them evenly with cocoa. Pour the mixture into them and put the chocolate soufflés with coffee to bake in a preheated 392°F (200 °C) oven for 10-12 minutes.
Optionally, serve sprinkled with powdered sugar.