Boil the water together with the salt and butter, then take it off the heat and pour the flour progressively, stirring quickly with a wooden spoon, then put it on the fire again until the composition comes off the bowl slightly. Put eggs one at a time and stir constantly. Grease a pan with butter and sprinkle a little flour and make the forms for the eclair, with the help of a cone with a diameter of about 1 cm, and the eclairs to be around 8-10 cm, they will swell a lot during baking, before putting them in the oven, grease them with a yolk.
Place in the preheated oven at 180C for about 30-35 minutes, until golden. Let them cool and in the meantime prepare cream.
Beat the yolks with the sugar, starch, vanilla and salt until they are lemon colored. Boil the milk and then pour over the egg mixture, stirring quickly. Put the bowl in which you boiled the milk on the fire and boil the cream stirring all the time so as not to make lumps until it thickens. Take the bowl off the heat and put the chocolate pieces and mix until it melts and mixes evenly with the cream.
When the cream has cooled, add the whipped cream and mix gently. Put the cream in a cone and start filling the eclairs that you have previously cut to one side.
For decoration, break the chocolate into small pieces and put in a bowl, boil the cream a little and then pour it over the pieces of chocolate. Wait a few seconds then mix gently. Using a spoon, place the chocolate on top of the eclairs. When they are ready, leave them in the fridge for a while before consuming them.