Line a baking sheet with parchment paper, set aside.
In a medium saucepan, add the water, butter, sugar, and salt.
Heat over medium heat, stirring often, until it comes to a boil. Reduce heat to low.
Add flour and cocoa powder to the saucepan and stir constantly with a rubber spatula until the dough comes together.
Remove the pan from heat and transfer the dough to a medium mixing bowl. Let cool for 8 minutes.
Add the eggs and vanilla extract to the mixing bowl. Beat until the dough comes together.
Transfer the dough to a large piping bag fitted with a large star-shaped tip and pipe 4-inch churros onto the prepared baking sheet. Freeze the churros on the baking sheet for at least 30 minutes.
Preheat the air fryer to 370 F.
Carefully transfer churros to your air fryer basket or trays and air fry them (in batches if necessary) for 12 to 15 minutes, until they are crispy.
Meanwhile, in a small bowl, combine granulated sugar, cinnamon, and cocoa powder.
Roll warm churros in the sugar mixture as soon as they come out of the fryer. Set aside.
Add the warm heavy cream, chocolate chips, and butter to a medium bowl and mix until the chocolate has melted and the mixture is smooth.
Serve warm churros with the chocolate dipping sauce as desired.