Boil 2 cups (500 ml) of water and add the butter with a pinch of salt. After the butter melts, pour in the flour all at once and stir until you get a smooth blend. Remove from the stove and add the eggs, which you've whisked separately, one by one while stirring nonstop.
Spray out elongated eclairs in a dry tray about 1 apart from each other. Bake the eclairs until ready in a moderate oven and let them cool with the oven door open.
For the cream, combine the flour and milk, stir and boil until thickened on low heat. Then, add the yolks, sugar, vanilla and beaten to snow whites in succession. Whisk with the whites carefully from the bottom up.
Cut the cooled eclairs with a sharp knife on one side and fill them with cream.