Preheat your oven to 180°C (356°F). In a mixing bowl, combine all-purpose flour and unsweetened cocoa powder, setting this dry mixture aside. In another bowl, beat the eggs at medium-high speed, gradually adding sugar. Continue beating until the mixture thickens and becomes foamy, about 10 minutes. Carefully fold the flour-cocoa mix into the eggs, preserving the airiness, then pour into a greased baking pan. Bake for 15 minutes and let it cool for at least 8 hours, or overnight for best results.

In a separate bowl, combine 500 ml of milk with cornstarch and cocoa powder, and set aside. In a saucepan, heat the remaining milk with sugar and pure vanilla extract until it steams gently. Gradually whisk in the cocoa-cornstarch mixture, stirring continuously until thickened, about 1-2 minutes. Once the custard mimics a pudding consistency, transfer it to a bowl and allow it to cool for at least 2 hours.

For the whipped topping, take your heavy whipping cream and whip it in a chilled bowl until soft peaks form. Gently incorporate sugar and unsweetened cocoa powder until firm peaks have formed.

Once your cake has fully cooled, slice it in half horizontally. Place one layer on a serving plate and spread ⅔ of the custard cream on top evenly. Gently place the second half of the cake over the custard layer and finish with the remaining custard cream, smoothing it out.

Melt butter and unsweetened cocoa powder together in a saucepan over low heat, stirring until smooth. Remove from heat and blend in honey. Pour this cocoa glaze over the assembled cake.

Take your chilled Sokolatina out of the fridge and cut it into squares. Decorate with a dollop of the remaining whipped cream on each slice.