Preheat the oven to 350°
Melt the cup sugar in a medium saucepan over medium heat, stirring frequently, until it turns into a dark caramel amber color, 9 to 10 minutes. Carefully pour the amber colored caramel into the flanera.
Place the heavy cream in a microwave safe measuring cup and microwave for 1 minute or until very hot, near boiling.
To a large mixing bowl, add the dark chocolate chips and pour the hot heavy cream. Whisk until the chocolate chips have fully melted.
While whisking the chocolate, slowly pour in the condensed milk, evaporated milk, whole eggs, egg yolks, brewed espresso coffee, salt and vanilla.
Place the flanera in a 9x13 baking dish. Using a strainer, pour the flan mixture into your prepared flanera.
Fill the baking dish with warm water halfway up the sides to create a water bath/baño Maria. Cover the flan with the lid of the flanera or with aluminum foil.
Bake the flan for 75 minutes or until the center jiggles slightly when shaken. 40 minutes into baking, add in more water to the water bath. Let the flanera cool in the water bath, then refrigerate for at least 2 hours.
When ready to serve, run a paring knife around the edge of the ramekin, place a serving platter or large plate over the top, and invert the ramekin. Give the flan mold a few taps with a spoon to help release the flan from the mold. Liquid caramel will drip down the sides of the flan mold, so careful when lifting as to not make a mess.