Step 1:Prepare the Churro Dough

• In a medium saucepan, combine the water, sugar, salt, and vegetable oil. Bring to a boil over medium-high heat.
• Once the mixture boils, remove from heat and immediately add the flour.
• Stir vigorously until the mixture forms a ball of dough and pulls away from the sides of the pan.

Step 2:Pipe the Churros

• Transfer the dough into a piping bag fitted with a large star tip (to give the churros their characteristic ridged texture).
• Heat about 2 inches of vegetable oil in a deep skillet or frying pan to 375°F (190°C). You can test the oil by dropping a small piece of dough into it; if it sizzles and browns quickly, the oil is ready.
• Pipe strips of dough directly into the hot oil, cutting them off with scissors or a knife to the desired length (usually about 4-6 inches). Be careful not to overcrowd the pan.

Step 3:Fry the Churros

• Fry the churros until golden brown and crispy, about 2-3 minutes per side. Use a slotted spoon or tongs to turn them as they cook.
• Remove the churros from the oil and drain on paper towels.

Step 4:Coat the Churros

• While the churros are still warm, roll them in a mixture of sugar and ground cinnamon (if using) until evenly coated. Set aside.

Step 5:Make the Chocolate Sauce

• In a small bowl, mix the cornstarch with a little bit of the milk to make a smooth slurry.
• In a medium saucepan, combine the remaining milk, chopped dark chocolate, sugar, and a pinch of salt. Heat over medium-low heat, stirring constantly, until the chocolate is melted and the mixture is smooth.
• Add the cornstarch slurry to the chocolate mixture and continue to cook, stirring constantly, until the sauce thickens to your desired consistency (about 3-5 minutes). The sauce should be thick enough to coat the back of a spoon.

Step 6:Serve

• Serve the warm churros with the thick, hot chocolate sauce for dipping. Enjoy immediately.