Cook the bacon pieces in a heavy skillet over medium heat until they are brown. Remove, set aside. Add olive oil to the bacon greased pan and add onion and cook until tender. Put bacon back on. In a separate bowl mix parsley, ricotta, prosciutto and egg yolks. Cook the spaghetti the way you like it. Drain. In a large bowl toss the noodles with the parsley, cheese-prosciutto mixture. Pour on the onion-bacon mix. Sprinkle grated parm on top. :o)