Ingredients
Pan sizes, times and temperatures in the method are not scaled.
Chocolate sponge
Rum syrup
Chocolate cream
Fondant glaze
Method
Sponge. Heat the oven to 350°F (180°C) and line a 25 × 35 cm (10 × 14 inch) pan. Beat the egg whites with the salt to stiff peaks, adding the granulated sugar (200 g1 cup) gradually. Fold in the yolks. Sift the all-purpose flour (100 g¾ cup + 1 tbsp) and cocoa powder (50 g½ cup + 2 tbsp) over and fold them in.
Bake 25 minutes. Cool.
Syrup. Heat the water (100 ml7 tbsp) and granulated sugar (50 g¼ cup) until dissolved. Cool and add the rum (2 tbsp).
Cream. Beat the eggs (4) with the granulated sugar (200 g1 cup) over simmering water until thick, then cool. Melt the dark chocolate (200 g) and cool. Beat the butter (250 g1 cup + 2 tbsp) until creamy. Combine all three and add the rum (2 tbsp).
Assembly. Slice the sponge into 2 layers and soak both with the syrup. Spread cream between the layers and on top. Refrigerate until firm.
Glaze. Mix the powdered sugar (200 g1⅔ cups), cocoa powder (16 g3 tbsp), hot water (30 g2 tbsp), butter (14 g1 tbsp) and rum extract (1 tsp) until smooth and pourable. Pour it over the cake and spread evenly. Let it set, then cut into squares.