Confetteria Moriondo e Gariglio
Via di Pie' di Marmo 21-22
Rome, Italy

The oldest chocolatier in Rome not far the Pantheon, down the side street next to the Chiesa di Santa Minerva.  Go early for a good selection.  Not cheap, but worth every Euro, especially for a special gift for your relatives in Rome.  Everyone knows this shop and its quality.  Helpful staff that speak some English.