Combine sugar, chocolate, coffee, and butter in a large saucepan.

Heat over low heat, stirring constantly, until melted and smooth.

Remove from heat and transfer the mixture to a large mixer bowl.

Whisk the eggs in a separate bowl.

Slowly pour the whisked eggs into the warm chocolate mixture while mixing on low speed.

Mix until just blended and the batter is uniform.

Pour the batter into a buttered and foil-lined 9-inch springform pan.

Bake at 350 degrees Fahrenheit (175 degrees Celsius) for 1 hour, or until almost set.

Remove the cake from the oven and let it cool on a wire rack.

Allow the cake to cool completely.

Refrigerate the cake overnight.

Slice the cake and garnish with whipped cream before serving.