In a large Dutch oven or countertop fryer using a high heat thermometer, bring the canola oil to 375 degrees F.
For the chocolate sauce: Bring a double broiler to a simmer over medium-low heat. Carefully melt the chocolate. Remove from the heat. With a wooden spoon or heat resistant spatula, stir in the heavy cream until the sauce is smooth. Set aside.
For the churros: Set a large saucepot over medium heat. Add 1 cup water, the butter, sugar and salt. Bring to 155 degrees F, then dump in the flour and stir with a wooden spoon to incorporate and remove lumps, about 1 minute.
Using the spoon, add the eggs into the batter one at a time, beating after each addition, until fully incorporated. Spoon the batter into a pastry bag fitted with a star tip and carefully pipe into the heated oil, forming 6-inch strips or free form shapes. Do not overcrowd the pot. Fry for 3 to 5 minutes, turning once as the underside browns. Remove with a spider or slotted spoon and drain on paper-towel-lined sheet tray or plate.
To finish: Working quickly, combine the sugar and cinnamon together in a large mixing bowl. Gently add the hot churros, tossing to coat. Serve with the chocolate dipping sauce.