Preheat your oven to 425 F. Put a large frying pan on a medium heat and add a good lug of olive oil. Add the diced onions and fry for 10 minutes or until softened, then remove from the heat and let cool completely. Put the ground meat into a bowl with mustard, oregano, cumin, coriander, bread crumbs, eggs, a good pinch of salt and pepper, and the cooled onions. Use clean hands to really scrunch it all together well, then divide the mixture into 8 patties
Wet your two hands with water. Pick each patty up, one at a time, and roll into a baseball-sized ball. tick your thumb deep into the ball to make a pocket, then stuff in a good pinch of grated cheese. Cup, pack, and pat the meat around the cheese, using your hands to mold it back into a ball. you'll soon get the hang of it. Place the balls in a large oiled Dutch oven or roasting pan, drizzle over a good lug of olive oil, then bake for about 25 to 30 minutes, until golden and sizzling
Meanwhile, use a paper towels to wipe out the pan you cooked your onions in, and put it back on a medium heat with a few lugs of olive oil. Add in the onion, bell peppers, garlic, fresh chiles, and paprika and fry gently for about 15 minutes. Stir in the Worcestershire sauce, ketchup, vinegar, molasses or sugar, mustard, coffee, and tomatoes, and bring everything to a boil. Turn the heat down to medium-low and simmer for 20 minutes, until the sauce has thickened. It should be thick and delicious, but if you'd like it a bit thicker, just turn the heat up and cook for a few more minutes
Remove the cooked meatball from the oven when they're ready and spoon away as much of the fat from the pan as you can. pour your chile sauce over the top, and return the pan to the oven for 5 more minutes. Finely chop your parsley, sprinkle over, and serve with a spoonful of rice or mashed potatoes and a lemony green salad