Instructions

1. 1
   Melt the chopped chocolate and coffee together in a heatproof bowl set over a pot of barely simmering water (a double boiler), stirring until uniform.
2. 2
   Remove from heat and beat in the softened butter one tablespoon at a time.
3. 3
   Whisk the egg yolks with 1/2 cup of the granulated sugar until the mixture becomes pale yellow, thick, and forms a ribbon when lifted.
4. 4
   Gently fold the warm melted chocolate mixture into the beaten egg yolks until fully integrated.
5. 5
   In a separate clean bowl, whip the egg whites with a pinch of salt until they form soft peaks.
6. 6
   Gradually sprinkle in the remaining 1/4 cup of sugar , continuing to whip until stiff, glossy peaks form.
7. 7
   Stir one-quarter of the whipped egg whites directly into the chocolate base to lighten its texture.
8. 8
   With a delicate hand, fold the remaining egg whites into the chocolate mixture using a rubber spatula just until no white streaks remain.
9. 9
   Pour into serving glasses and chill for at least 4 hours before serving.