For the churros:
For the chocolate dipping sauce:
In a medium saucepan, combine the butter, water, sugar and salt over medium-high heat. Stir frequently. Bring the mixture to a boil. Remove from the heat and transfer to a food processor (a stand mixer would also work.) Add in the flour. With the feed tube open to vent steam, pulse (or mix) briefly to incorporate the flour. While continuing to mix, gradually pour in the eggs in a slow, steady stream until fully incorporated and the mixture is just smooth.
Heat a large pot of canola oil (at least 2-3 inches deep) to 375˚ F. While the oil is heating, transfer the batter to a pastry bag fitted with decorative tip. When the oil has reached the desired temperature, pipe lengths of the batter into the oil, using scissors to snip each length off into the pot. Keep the churros only in a single layer and avoid crowding them. Fry, flipping once, until light golden brown, about 2-3 minutes per side. Remove from the oil with a slotted skimmer and transfer to a rack lined with paper towels. Repeat with the remaining batter. Be sure the oil returns to 375˚ F before adding a new batch.
In a shallow bowl or plate, combine the sugar and the seeds scraped from the vanilla bean pod. Massage together until the vanilla bean is evenly distributed in the sugar. Stir in the cinnamon. Dredge the cooked churros in the cinnamon-sugar mixture, shaking off the excess.
To make the chocolate sauce, place the chocolate in a small bowl. Bring the heavy cream to a simmer, pour over the chocolate, and let stand 2 minutes. Whisk together until a smooth ganache forms. Whisk in the butter until fully incorporated. Reheat as necessary to keep liquid for dipping.