Steps

• Bring the water, butter, and salt to a boil.
  Remove from heat and add all the flour at once, previously sifted.
  Stir vigorously and quickly with a wooden spoon to avoid lumps forming.
  The dough should be compact and homogeneous.
  Return to the stovetop and over low heat, continue stirring to dry out the dough.
  This will take 1 or 2 minutes at most, until the dough detaches from the pot.
  Place the dough in the stand mixer bowl and let it run with the K beater until it’s lukewarm.
  Add the eggs one at a time, ensuring they are well incorporated each time.
  Fill the piping bag.
  On a slightly buttered baking sheet, form the puffs.
  Bake the puffs in a preheated oven at 450°F.
  After 8-10 minutes, lower the temperature to 400°F, slightly open the oven door to let the steam out.
  After another 10 minutes, lower it to 350°F and continue baking for about 10 minutes.
  Remove them from the oven and let them cool on a rack.

• Chop the chocolate coarsely and place it in a bowl. Split the vanilla bean in half and scrape out the seeds with a knife.
  Pour the milk into a pot with the vanilla bean, heat over low flame until boiling.
  Place the vanilla seeds with the egg yolks and sugar in a bowl and mix well with a whisk.
  Add the starch and a pinch of salt.
  Pour the cream into the hot milk and stir with a whisk.
  Cook while stirring continuously for about 5 minutes over low heat.
  Pour the hot cream over the chopped chocolate and mix with a spatula.
  Cover with plastic wrap in contact and cool quickly in ice water, then transfer to the fridge for at least 3 hours.

• Pour the cream into a bowl with the powdered sugar and the vanilla bean seeds.
  Beat with an electric mixer at maximum speed until the cream is glossy and semi-whipped.
  Store in the fridge.

• Pour 1/3 of the semi-whipped cream into the chocolate cream bowl and stir with a whisk to smooth the mixture and make it homogeneous.
  Then add 1/3 of the cream, but fold it in with a spatula using upward movements to prevent it from deflating.
  Once incorporated, add the remaining cream in the same way.
  Store in the refrigerator covered with plastic wrap in contact until use.

• Cut the puffs in half and fill them with chocolate diplomat cream using a piping bag.
  Close with the other half and dust with cocoa powder.