1. In a saucepan, combine water, butter, sugar, and salt. Bring to a boil.
2. Remove from heat and add Prima Plain Flour all at once. Stir quickly until a dough forms and pulls away from the sides (about 1–2 mins).
3. Let the dough cool slightly.
4. Transfer the dough to a mixing bowl and let it cool for another 5 mins.
5. Add eggs one at a time, beating well after each addition until the mixture is smooth, glossy, and pipeable.
Note: The dough should be sticky but not runny.
6. Mix in the vanilla extract.
7. Fill a piping bag fitted with a medium–large star tip.
8. Heat oil to 170–180°C.
9. Pipe 8–10cm strips of dough directly into the oil, cutting each strip with scissors.
10. Fry for 2–3 mins per side or until golden brown.
Note: Work in small batches.
11. Drain on paper towels. While still warm, toss the churros in sugar and cinnamon.