Mix the 4 egg yolks with 2.1 oz of sugar.
Whip the 4 whites into peaks with 2.1 oz of sugar.
Soften the gelatin in cold water.
Whip the cream.
Combine the whipped cream with egg yolks.
Melt the gelatin in the coffee and add to the mixture.
Add the whipped whites by stirring from the bottom up.
Pour the mixture into a rectangular plumcake mold.
Cover it with the slice of sponge cake and soak it with the sweetened coffee.
Place in the freezer for 6 hours.