Line a baking sheet with 3 or 4 layers of paper towels. Place a large deep sided, heavy skillet on the stove top and add oil until 1/2 to 3/4-inches deep. Assemble pastry bag with star tip (1M), cookie press or churro press.
Combine 3/4 cup water, oil, 1-1/2 tablespoons of the sugar and salt in a deep sided saucepan over medium high heat. Stir to combine and bring to a boil. Reduce heat to medium, add flour and stir well using a wooden spoon. Continue to stir and cook for 1 minute or until dough is very stiff and forms a ball; remove from heat and allow to cool for 5 to 10 minutes.
Add yeast and remaining 1-1/2 teaspoons sugar to the 1/4 cup warm water, stir to dissolve and set aside.
Add eggs one at a time to the dough in a medium bowl. Beat with an electric mixer on medium-high speed for 1 to 1-1/2 minutes. Dough may appear lumpy at first. Pour in the yeast mixture and continue mixing for 1 to 2 minutes or until the dough is very smooth; dough should be very thick and sticky.
Heat oil over medium heat to 375°F.
Transfer the dough using a rubber spatula into the pastry bag or cookie press fitted with a star tip (1M works best). **NOTE: Do not substitute any other shape or tip. Churros can explode when cooked in hot oil if not star-shaped. Pipe the dough into the hot oil in 6-inch long strips. Fry in batches of 3 or 4 at a time allowing oil temperature to recover between batches. Cook for 1 to 2 minutes per side or until golden brown. Transfer cooked churros onto prepared baking sheet to cool. Sprinkle with cinnamon sugar, if desired.
In a saucepan combine sugar, corn starch, and milk. Turn heat to medium high, stirring constantly bring to a boil ( approx. 5-8 minutes) and allow to boil for one minute. Remove from heat and stir in chocolate until melted and very smooth. Serve with warm churros.