Prepare the batter: In a medium bowl, whisk together the flour, sugar, baking powder, salt, and cinnamon (if using).
Mix the wet ingredients: In a separate bowl, beat the egg, then add the milk and vanilla extract. Whisk until smooth.
Combine: Gradually add the wet ingredients to the dry ingredients, stirring until the batter is smooth and lump-free. The consistency should be slightly thick but pourable.
Heat the oil: In a deep skillet or fryer, heat about 2 inches of vegetable oil to 375°F (190°C).
Pipe the batter: Transfer the batter into a squeeze bottle or piping bag with a small round tip. Pipe long, thin lines of batter directly into the hot oil, cutting them off with scissors.
Fry to perfection: Fry for about 2-3 minutes, flipping halfway through, until the fries are golden brown and crispy.
Drain: Remove the fries with a slotted spoon and place them on a plate lined with paper towels to absorb excess oil.
Dust and serve: Generously dust with powdered sugar and serve warm with your favorite dipping sauces.