Preheat oven to 325 degrees F. Trim fat from ribs. In an extra-large oven-going skillet heat oil over medium-high heat. Add ribs; cook until brown on all sides, working in batches if necessary. Remove ribs from skillet.
Add onions, celery, and carrot to skillet. Cook over medium heat for 5 to 7 minutes or until onions are golden, stirring occasionally. Add garlic; cook and stir for 1 minute more. Add wine, stirring to scrape up any crusty brown bits from bottom of skillet. Add bay leaves, espresso powder, thyme, rosemary, and pepper. Stir in broth. Bring to boiling; return ribs to skillet. Cover skillet and transfer to oven. Bake for 3 to 3 1/2 hours or until ribs are tender. Transfer ribs to a deep serving platter; cover and keep warm.
For sauce, strain cooking liquid through a fine-mesh sieve; discard vegetables. Skim fat from strained liquid. Return liquid to skillet. Bring to boiling over medium-high heat; reduce heat to medium. Simmer, uncovered, until liquid is reduced by half. Stir in whipping cream. Remove from heat. Stir in chocolate until melted.
Pour sauce over ribs. If desired, sprinkle with green onion. Serve over Polenta.
In a large saucepan bring milk just to a simmer over medium heat. In a medium bowl combine cornmeal, water, and salt. Stir cornmeal mixture slowly into hot milk. Cook and stir until mixture comes to a boil. Reduce heat to low. Cook for 10 to 15 minutes or until mixture is very thick, stirring occasionally. (If mixture is too thick, stir in additional milk.) Stir in butter or margarine until melted.