You must definitely involve parsley somehow...perhaps get a flower box (like the kind you would get long-stemmed roses in), put the engagement ring at the bottom of the box, and fill it with parsley. Arrange for the maitre'd to somehow deliver this during that lull after dinner but before dessert (if you're worried about the safety of the ring, keep it on you, excuse yourself to go to the restroom, and use the chance to put it in the box then). Give your fiance the box of parsley and tell her, "I'd like to do it for real this time." Let her find the ring beneath the parsley, and then propose.
Don't forget to also arrange for champagne to be brought to your table immediately following the successful proposal.
