In a saucepan, boil the water together with the oil and salt. Mix the flour with the vanilla sugar. When the water boils, take the pan off the heat and add the flour. Stir vigorously until the composition comes off the pan easily. Add eggs one at a time, mixing one by one with a mixer after each, until incorporated. With a spoon, put the composition in a bag or posh and shape the eclairs in a tray lined with paper. Add enough composition so that they do not come out very low. Bake the shells at 180 ° C for 25 minutes.
Put eggs in a saucepan and beat well. Add sugar and vanilla sugar. Then pour the flour and mix until smooth. Heat the milk and gradually add it over the previously prepared composition. Put the pot on the fire, add the vanilla essence and let the composition thicken, stirring constantly so that it does not stick. When the composition has thickened enough, add the chopped butter and mix until it has melted.
Mix all the ingredients and put them in a bain marie until they melt. You can also put it directly on the fire, but be very careful not to overheat it too much. Remove from the heat when the chocolate begins to melt and stir continuously until all the ingredients have melted and incorporated. If necessary, put it on the fire for a few seconds.
If you want, you can also put whipped cream on top of the vanilla cream.