Combine the water, butter, sugar, and salt in a medium-sized saucepan. Heat the saucepan over medium heat until the mixture reaches a boiling point.
Lower the heat and add all the flour at once. Stir vigorously using a wooden spoon until the mixture forms a smooth ball and separates from the sides of the pan. This process should take approximately 2-3 minutes.
Transfer the dough to a mixing bowl and allow it to cool slightly for 5 minutes.
Gradually add the eggs, one at a time, and beat well after each addition. The dough should become smooth and shiny.
Heat vegetable oil in a deep fryer or large pot to a temperature of 175°C (350°F).
Fill a piping bag fitted with a large star tip with the dough.
Pipe rings of dough onto a sheet of parchment paper or directly into the hot oil. Each cruller should have a diameter of approximately 8-10cm (3-4 inches).
Fry the crullers in batches, flipping them once, until they turn golden brown and expand in size. This should take around 4-5 minutes per side.
Use a slotted spoon to remove the crullers from the oil, allowing excess oil to drain on a paper towel-lined plate.
In a separate bowl, prepare the glaze by whisking together the icing sugar, milk, and vanilla extract until the mixture is smooth and well combined.
Dip each cooled cruller into the glaze, ensuring that any excess glaze drips off.
Place the glazed crullers on a wire rack and let them set for approximately 10 minutes.
Enjoy the French Crullers while they are fresh! Note that they are best consumed on the same day they are made for the optimal texture and taste.