Whisk the egg whites to stiff peaks, adding the sugar gradually, then fold in the yolks in parts. Sift the flour with the cocoa powder and gently fold in with a spatula.

Pour the batter into the pan and bake for 30-35 minutes. Test for doneness with a toothpick: it should come out dry. Remove the sponge and let it cool completely.

For the charlotte cream, whisk the egg with the condensed milk and water in a saucepan, bring to a gentle boil until thickened, then remove from heat and let cool.

Whip room-temperature butter until fluffy, add the cooled condensed milk mixture, cocoa powder, and brandy for flavor. Whip again - the cream is ready.

Slice the sponge into three layers. Spread cream on two layers, and apple preserves on the top one. Chill the cake in the fridge.

For the fondant, boil a sugar syrup (sugar and water in a 3:1 ratio) to 120°C - without a thermometer, that's roughly 7-10 minutes of boiling. Let it cool slightly, then whisk until pale and thickened to the right consistency.

Add cocoa powder to the fondant and stir with a spatula until smooth. Spread it over the top of the cake quickly. Put the kettle on and wait for your guests!