Sift the flour into a dry bowl, preheat the oven to 200°C. Line a baking tray with baking paper and boil the milk.
Bring water to a boil in a small saucepan. Then add butter and boil again. Gradually add flour in small portions, stirring continuously. Remove from heat and cool to room temperature.
Adding one egg at a time, beat the resulting dough at medium speed of the mixer. The dough should have a fairly thick consistency, add a little more flour if necessary.
In a deep bowl, combine the egg, sugar and flour, beat the resulting mixture with a whisk or mixer at medium speed. Add hot boiled milk to the egg mixture in portions, stirring continuously. The mixture should thicken as you heat and stir.
Cool the milk-egg mixture to room temperature and mix with the butter. Beat with a mixer at high speed until smooth. Using a clean piping bag, place the cream into the dough pieces.
Sprinkle the finished eclairs with powdered sugar.