1. Place the water, sugar, oil and butter into a pan and bring it to the boil
2. Add the flour in and mix until well combined.
3. When ready, start adding the eggs one by one and mix properly until you reach a nice and smooth consistency.
4. Transfer mixture to a piping bag fitted with a large open star tip.
5. In a large pot over medium heat, add enough oil to come halfway up the sides and heat to 190°C. Holding the piping bag a few inches above the oil, carefully pipe churros into 6" long ropes. Use kitchen scissors to cut off dough from piping bag.
6. Fry until golden, 4 to 5 minutes, turning as necessary. Fry 3 to 4 churros at a time and let oil come back to 190°C before each batch. Remove churros with a slotted spoon or tongs and immediately roll churros in cinnamon sugar (if desired), then place on a cooling rack.

For The Chocolate Dipping Sauce

1. Place chocolate chips in a medium heatproof bowl. In a small saucepan over medium heat, bring double cream to a simmer. Pour hot cream over chocolate chips and let sit 2 minutes. Add cinnamon and salt and whisk to combine