To make the churros, add the water, butter, and salt to a medium saucepan and heat over medium high heat, stirring occasionally, until the butter is melted. Remove from heat. Add the flour all at once and stir to form a dough. Add the eggs one at a time, stirring well after each addition, until the dough is smooth and satiny. Scoop the mixture into a piping bag fitted with a large open star tip.
Heat the oil in a pot over medium heat until it reaches 365 degrees. While you’re waiting for the oil to heat, prepare an area to drain the churros. I usually use a cooling rack lined with paper towels.
Mix together the sugar and cinnamon in a shallow dish and set aside.
Carefully pipe six inch lengths of dough into the oil, being careful not to crowd the pot. Let cook 2-3 minutes on each side, or until golden brown. Remove and let drain for 1-2 minutes, then roll in the cinnamon sugar mixture.
To make the raspberry sauce, whisk together the corn starch, sugar, and water in a medium saucepan. Add the raspberries and stir to combine. Heat over medium heat, stirring frequently, until the mixture reaches a boil. Let boil one minute, then remove from heat. Strain through a fine mesh strainer (if desired) to remove the seeds.