Cook over a low heat, stirring constantly until smooth and thick.
Beat in the eggs one at a time, mixing well each time.
The dough should be uniform.
Use a spoon or a bag to place medium-sized balls on a baking sheet covered with parchment. Bake at 200 degrees for the first 10 minutes, then at 180 degrees for another 15-20 minutes. These are the kind of buns you get.
For the cream, heat the milk, beat in the yolks.
Add the sugar, vanilla sugar and flour and cook until thick, stirring constantly. Cool.
In a food processor, place the whisk attachment and whisk the cream together with the butter and cognac.
Fill the rolls with cream using a pastry syringe.
For the glaze, melt the chocolate in a water bath, add the milk and mix well. Pour the icing over the buns and decorate as desired.