Preheat oven to 350°F (180˚C).
In a saucepan over medium heat, add the butter, brown sugar, and water to a saucepan and bring to a boil.
Turn off the heat and stir in the flour and salt.
Then mix in the vanilla and egg (one at a time if using multiple eggs).
Transfer mixture to a piping bag with a 5 point or star tip.
Pipe out thick 3 to 4-inch strips of batter onto a baking sheet covered with parchment, using a knife to release each piece from the piping tip, if needed.
Bake for 10 minutes, then switch to low broil until golden brown.
In a bowl mix together the cinnamon and granulated sugar until fully combined.
Toss each churro in cinnamon sugar before serving.