Make the cinnamon sugar: In a shallow bowl, mix 1/2 cup granulated sugar with 1–2 teaspoons ground cinnamon. Set aside.
Start the choux dough: In a medium saucepan, add 1 cup water, 8 tablespoons (1 stick) unsalted butter, 1 tablespoon granulated sugar, and 1/4 teaspoon salt.
Bring to a gentle boil over medium heat, stirring to melt the butter.
Add the flour: Once boiling, remove from heat and add 1 cup all-purpose flour all at once. Stir quickly with a wooden spoon, then return to medium heat and cook, stirring constantly, for 1–2 minutes until the dough forms a smooth ball and a thin film forms on the pan.
Cool slightly: Transfer the dough to a bowl. Let it cool for 5 minutes so the eggs don’t scramble.
It should be warm, not hot.
Beat in the eggs: Add 1 teaspoon vanilla. Beat in 2 large eggs, one at a time, mixing thoroughly after each until the dough is smooth and glossy. It should be thick but pipeable.
Prep the air fryer: Preheat to 375°F (190°C) if your model requires preheating.
Lightly brush or spray the basket with neutral oil. Cut parchment to fit the basket and poke a few holes for airflow, then lightly oil the parchment too.
Pipe the churros: Spoon the dough into a piping bag fitted with a large star tip (a French star tip gives the best ridges). Pipe 4–6-inch lengths onto the parchment, leaving space between.
Use scissors or a knife to cut the dough cleanly.
Brush lightly with oil: For extra browning, lightly brush the tops with neutral oil or melted butter.
Air fry: Cook for 8–10 minutes until puffed and deep golden, turning once halfway if your air fryer browns unevenly. Work in batches; don’t overcrowd.
Coat in cinnamon sugar: While hot, toss the churros in the cinnamon-sugar mixture. If needed, brush with a touch of melted butter first so the sugar sticks.
Make the chocolate sauce: In a small saucepan or microwave-safe bowl, heat 1/2 cup heavy cream until steaming (not boiling).
Pour over 1 cup chocolate chips or chopped chocolate. Let sit 1 minute, then stir until smooth and glossy. Add a pinch of salt and optional 1/4 teaspoon espresso powder or a dash of vanilla.
Serve: Plate the churros warm with the chocolate sauce on the side.
Sprinkle any extra cinnamon sugar on top.