In a large bowl, add the egg yolk, the whole egg, the sugar, the cocoa powder and mix everything very well.
Add the milk, turn on the heat and stir everything very well until it starts to boil.
Next, dissolve the cornstarch in the milk, add it to the saucepan and keep stirring until it thickens and turns into a smooth cream.
Add the butter, stir until it melts and set aside until it reaches room temperature.
Finally, add the dried plums cut into smaller pieces and mix to combine.
In a medium bowl lined with plastic wrap, add 2 tablespoons of the chocolate cream and spread it all over the bowl.
Add 2 more tablespoons of the cream and cover with chocolate biscuits.
Then make another layer with the cream and cover with more chocolate biscuits.
Repeat this process with all the cream, finishing with a layer of biscuits.
Cover with plastic wrap, take the dessert to the fridge and let it chill for at least 2 hours.
After this time has passed, unmold the dessert and, in a medium bowl, add the semisweet chocolate.
Place it in the microwave on high power and melt it in 30-second intervals always stirring in between until fully melted.
Next, drizzle the melted chocolate we prepared over the dessert, creating a spiral pattern all around.
Take it back to the fridge and let it chill for another 15 minutes.
Serve.