Position the oven rack to the center and preheat to 325 degrees F.
Soak the ancho chiles in the hot water until soft, about 30 minutes. Strain through a fine mesh sieve, reserving the liquid separately. Discard stems and seeds. Transfer the chiles to a blender along with the onion, garlic, dark brown sugar, dried oregano, chicken stock, reserved chile soaking liquid, and process to form a smooth puree.
Heat 2 tablespoons of the oil in a 6-quart or larger Dutch oven (large enough to cook the ribs in one even layer) over medium-high heat. Using paper towels, pat the ribs dry and season with 2 teaspoons of the salt and the black pepper. Add 1/2 cup of the flour and Essence to a resealable 1-gallon plastic food storage bag. Place the ribs in the bag a few pieces at a time and shake until well coated with flour. Remove the ribs from the bag and, working in batches if necessary, cook the ribs until nicely browned and caramelized on both sides, 8 to 10 minutes. Transfer the short ribs to a baking sheet and set aside until ready to use.
Lower the heat to medium low. Add the remaining 1/2 cup of oil and whisk in the remaining 1/2 cup flour. Cook, stirring constantly to reach every portion of the bottom of the pot to scrape up the browned bits. Continue cooking and stirring constantly until the roux reaches the color of milk chocolate. Carefully add the chile puree (mixture will splatter!) and cook, stirring, until fragrant, about 5 minutes.
Add the instant espresso, the beef stock, the cinnamon stick, bay leaves and the remaining 1 teaspoon of salt, and stir to mix well. Return the short ribs to the pot, meaty part facing down, and bring to a boil. Cover with the lid, transfer to the oven, and cook until the ribs are very tender, about 2 1/2 hours.
Remove from the oven and skim any fat that has risen to the surface, if desired. Serve over rice, mashed potatoes, grits, or polenta.
Yield: about 6 servings