In a 1 liter saucepan, boil water, fat and salt. When it first boils, set aside the pan and add all the flour once, stirring vigorously. We pass on the fire again, but preferably not directly on the flame. Stir a few more times until the dough comes off the pan. Remove from the heat and leave to cool a bit. When it is almost cold, add the eggs one by one, mixing well after each one.
On a large tray lined with baking paper we will put piles of dough (with a teaspoon or a pos), leave the distance between them because they will grow in the oven.
Put the tray in the preheated oven at 200 degrees.
Great attention: after 10 minutes after introducing them, reduce the heat (from 200 to 180 degrees), and do not open the oven for the first 20 minutes. It should be cooked for about 30 minutes, no less.
In a pot put eggs, flour and sugar and mix well, add milk and mix well. Cut the vanilla pod in half lengthwise and remove the seeds. We put them in milk. Put on low heat and stir continuously until it hardens.
Cover the pot with plastic wrap and cool quickly (in cold water).
Beat the whipped cream hard and mix with the cooled cream.
We fill the eclairs and put them cold on a plate covered with a foil so that they do not dry out. Before serving, they can be garnished with cream, plain whipped cream or chocolate.
The baked dough can be stored longer in hermetically sealed or frozen plastic sheets.