Preheat 2 inches of cooking oil in a large pot or dutch oven to 375℉.
In a medium size saucepan add the water, butter, sugar, vanilla, salt and cinnamon, stir to combine. Bring to a boil, water will start bubbling around the sides of the pan. Sugar will be completely dissolved in the water.
Remove from heat and add the flour. Stir to combine.
Add this dough to the bowl of a stand mixer.
Add in beaten egg. Mix completely using paddle attachment of mixer. It will take 2-3 minutes for the egg to combine with the dough, wait for dough to pull away from the edge of the bowl. Dough will be firm, and still slightly sticky, it will stick to the bottom of the mixing bowl.
Add dough to pastry bag (spray inside of pastry bag with cooking spray) fitted with star tip (Atecco 1M tip is my favorite!)
Squeeze out strips of dough 2 1/2 - 3 inches long into the hot oil, use scissors to cut the dough. Fry 3-4 strips of dough at a time to prevent crowding.
Fry in oil for 2-2.5 minutes, turn then continue frying. Fry churros for approximately 4 minutes, until golden on all sides.
Remove from oil, place on large baking tray lined with a wire cooling rack, allow to cool briefly, (I add the next batch of batter to the oil) then dip into the cinnamon sugar topping while still warm.
Serve warm with warm chocolate fudge sauce.