Preheat oven to 350ºF.
In a double boiler, melt chocolate with boiling water and coffee.
While chocolate is melting, beat 6 egg yolks with 1/4 cup of sugar, a pinch of salt, and vanilla extract until color turns pale.
Gradually whisk egg yolk mixture into the chocolate, moving quickly to avoid egg clumps. Set aside.
In a separate bowl, beat 6 egg whites until soft peaks form. Gradually add remaining 1/4 cup sugar and beat until stiff.
Fold egg whites into chocolate mixture.
Pour ⅓ of the batter into a greased round baking dish. Bake for 10 minutes, or until set. Do not over bake.
Keep the rest of the batter chilled and when cake is cool, spoon remaining batter on top of crust.
Cover well and freeze.