In a saucepan, combine the water, butter, sugar, salt, and vanilla extract. Bring to a gentle boil over medium heat.

Remove from heat and add the plain flour all at once. Stir vigorously until the mixture forms a smooth dough that pulls away from the sides of the pan.

Transfer the dough to a piping bag fitted with a large star nozzle.

Heat sunflower oil in a deep frying pan or pot over medium-high heat until it reaches 180°C (use a cooking thermometer for accuracy).

Pipe strips of dough directly into the hot oil, using scissors to cut them to your desired length. Be careful not to overcrowd the pan.

Fry the churros until golden brown and crispy, about 4-5 minutes, turning occasionally for even cooking.

Remove the churros from the oil using a slotted spoon and drain on a plate lined with kitchen paper to remove excess oil.

In a shallow bowl, mix together the caster sugar and ground cinnamon for coating.

While the churros are still warm, roll them in the cinnamon sugar mixture until evenly coated.

Serve immediately and enjoy your delicious homemade churros!