Steam cleaned mussels in a covered pot, using a small amount of water or white wine, until shells open. Remove mussels and set aside; discard any that don’t open. Reserve broth. Once mussels cool, split open and scoop out meat. Set aside. Reserve 12 of the largest half-shells and place the meat from two mussels into each half-shell. Place the shells face up in a shallow baking dish. In a separate bowl, combine bacon or sausage, onion, garlic or shallot, and olives, bind with a little olive oil, then spoon mixture onto each half-shell. Sprinkle with cheese and spices, then top with a few drops of olive oil. Bake at 400 F for 10 to 15 minutes; finish by broiling until cheese turns golden brown. Serve with fresh bread and the reserved broth as a dipping sauce. Serves two adults as an appetizer. Garnish with parsley and serve with sliced lemons, if available.