Clean mussels thoroughly. Discard any that do not close. Put them in a sauce pan with white wine and cook over high heat until the mussels open. Throw out any that do not open. Place the mussels in their half shells onto a baking sheet (do not discard the other half of the shell just yet). Chop up the prosciutto and mix in a bowl with bread crumbs, parsley, garlic, 1/2 of the olive oil, salt (easy on the salt) and pepper and the juice from the mussels. Mix all together. Put some of the mixture on each mussel in the pan. Add a little olive oil to each mussel. Place in oven on broil for about 2 to 3 minutes until the bread crumbs are golden (must be watched). Serve hot and with lemon, if preferred. If there is extra bread crumb mixture, you can add a can of chopped clams and put it in the other halves of the mussel shells to use it up; these take a little longer to cook.