Melt bittersweet chocolate in a double boiler over hot, not simmering, water (or in the microwave). Using a toothpick, dip a frozen Marshmallow Peep Chick in the chocolate, swirling until covered. Let excess drip off. Place a toothpick in a piece of Styrofoam so the Peeps can dry. Once dry, place the Peeps on tray and put in the refrigerator to harden.