Yields: 1 (9-inch) round cake or 12 individual cakes
10–11 oz. quality dark chocolate
1 tablespoon quality granulated coffee
10 large eggs, separated
¼ cup sugar plus ⅓ cup sugar, divided
2 tablespoons coffee or chocolate liqueur
4 tablespoons chopped walnuts, pecans, or hazelnuts
Preheat oven to 350°F.
In a double boiler, microwave, or a pan placed over a pot of boiling water, melt chocolate, mixing until smooth.
Remove from heat and stir in coffee.
In a bowl, beat egg yolks and ¼ cup sugar on high speed for about 8 minutes, until the mixture becomes a fluffy, light whipped cream.
In a separate bowl, beat egg whites and remaining ⅓ cup sugar on medium speed until the mixture becomes a firm foam.
Add melted chocolate to the egg yolk mixture and mix until combined. Add the liqueur.
Add yolk/chocolate mixture to the egg whites, using a spatula to gently combine in a folding motion.
Divide the mixture into 2 portions: ⅓ of the mixture and the remaining ⅔ of it. Refrigerate the smaller portion. Add chopped nuts to the larger portion and mix well. Pour into the pan and bake about 45 minutes.
Remove from the oven and refrigerate about 30 minutes.
After the cake has cooled and the center has sunken a little, remove the smaller portion from the refrigerator and gently fill the depression of the cake with it. Freeze at least 2 hours. (The cake can be stored in the freezer for up to 1 month.) Move the cake to the refrigerator about 30 minutes before serving.