For the Batter: In a small saucepan, bring water, butter, salt, sugar, and cinnamon to a simmer over high heat.

When butter has melted and sugar and salt have dissolved, lower heat to medium, add flour, and stir rapidly. The batter will form quickly as the flour absorbs the water mixture. Continue to cook over medium heat, stirring, for 1 minute.

Remove saucepan from heat and allow mixture to stand for 5 minutes. Add eggs one at a time to batter mixture, stirring until each is incorporated. The batter will be very stiff and look a bit like buttercream frosting.

Meanwhile, For the Topping and Chocolate Sauce: Mix sugar and cinnamon on a plate for dipping. In a saucepan over low heat, combine cream, chocolate, and corn syrup and stir frequently until chocolate begins to melt. Turn off heat and set chocolate mixture aside.

Preheat the waffle iron. (Set it to medium if it has temperature settings.) Coat both sides of the waffle iron with nonstick cooking spray.

Place about ¼ cup of batter on each section of waffle iron. Do not overstuff waffle iron—the batter will expand considerably. (Err on the side of using less batter before you see how much it spreads out and rises.) Close the lid and cook until churros are golden brown, 5 to 10 minutes. Transfer churros to a plate and repeat with remaining batter.

Brush churros with melted butter and then dip them in cinnamon sugar. Serve warm with chocolate sauce for dipping.