Prepare the Dough:

In a medium saucepan over medium heat, combine water, sugar, butter, and salt. Bring to a boil, then remove from heat. Add the cocoa powder and flour all at once and stir vigorously until the dough forms a ball.

Cool and Mix:

Let the dough cool for 5 minutes. Add the egg and vanilla extract, mixing until smooth and fully combined.

Heat the Oil:

Heat vegetable oil in a deep frying pan or pot to 375°F (190°C).

Pipe and Fry the Churros:

Transfer the dough to a piping bag fitted with a large star tip. Pipe 4–5-inch strips of dough directly into the hot oil, cutting with scissors. Fry 3–4 churros at a time for 2–3 minutes per side until crispy and cooked through. Remove and drain on paper towels.

Coat the Churros:

In a small bowl, mix granulated sugar, cinnamon, and cocoa powder (if using). Roll the warm churros in the mixture until evenly coated.

Serve and Enjoy:

Serve your chocolate churros warm with your favorite dipping sauce, such as chocolate ganache or caramel.