Mix the flour, sugar and part of the milk, beat until the lumps disappear.
Add the egg and beat.
Heat the rest of the milk on the stove and pour the egg mixture into it in a thin stream. Constantly stirring, cook until thick.
Add the butter and mix until it is completely dissolved.
Chop the cookies into crumbs, mix with cocoa powder, put the mixture in the custard and mix well.
Form cakes and roll them in crushed chocolate cookies or cocoa powder.
Put it in the refrigerator overnight.