1 cup (250ml) water
1/4 cup (56g) unsalted butter, diced into small cubes
1 Tbsp (13g) granulated sugar
1/4 tsp salt
1 cup (141g) all-purpose flour (scoop and level to measure)
1 large egg
1/2 tsp vanilla extract
Vegetable oil, for frying
1/2 cup (100g) granulated sugar
3/4 tsp ground cinnamon
For the coating whisk together 1/2 cup sugar and cinnamon in a shallow dish, set aside.
Heat about 1 1/2 inches vegetable oil in a large pot or deep skillet over medium-high heat to 360 degrees Fahrenheit. While oil is heating prepare batter.
Add water, butter, sugar and salt to a large saucepan, bring to a boil over medium-high heat.
Add flour reduce heat to medium-low and cook and stir constantly with a rubber spatula until mixture comes together and is smooth (a few lumps in it are fine).
Transfer mixture to a large mixing bowl, let cool 5 minutes.
Add vanilla and egg to flour mixture then blend immediately with an electric mixer. Blend until mixture comes together and is smooth (it will separate at first but keep mixing it will come together).
Transfer to a 16-inch piping bag fitted with a rounded star tip (no bigger than 1/2-inch).
Carefully pipe mixture into preheated oil, into about 6-inch lengths, cut end with clean scissors.
Let fry until golden brown, about 2 minutes per side. Transfer to paper towels to dry briefly then transfer to cinnamon sugar mixture and roll to coat.
Repeat process with remaining dough (frying no more than 5 at once). Serve warm with chocolate ganache or caramel sauce for dipping if desired.