Cinnamon Sugar: In a small bowl, mix the sugar and cinnamon just to combine. Set aside.
For the chocolate sauce: In a medium saucepan over medium heat, add the cream. Let it come to a gentle simmer, making sure it doesn’t boil. Place the chocolate in a heatproof bowl, then pour the hot cream over the chocolate and cover the bowl with plastic wrap. Allow to sit for 4 minutes, or until the chocolate is melted. Remove the plastic wrap, and whisk or stir to combine. Set aside.
Churros Dough: In a small saucepan over medium heat, combine the water, sugar, salt, and vegetable oil. Bring to a boil, then remove the pan from the heat. Using a wooden spoon, beat in the flour until thick paste forms. Return the pan to the heat, and cook for another minute.
Heat the oil in a heavy-bottomed pot or wok over medium-high heat to 375°F (191°C). Line a baking sheet with paper towels.
Place the dough into the piping bag. Pipe dough about 2 1/2 inches (6 cm) in length into the oil, use scissors to cut the dough. Do 3 or 4 at a time so as not to overcrowd the pot. Deep-fry until golden brown and crispy, about 4 minutes. Remove using a slotted spoon or spider and let drain on the paper towel–lined baking sheet. Immediately toss with the cinnamon sugar to ensure the coating will stick. Repeat with the remaining batter.
Serve warm or at room temperature with the chocolate sauce.