1Melt the butter in a medium saucepan over low heat. Remove from the heat and add the chocolate. Let stand until the chocolate is softened, about 3 minutes. Whisk until the chocolate is smooth and melted. Whisk in the egg. Fold in the graham crackers.
Cover loosely with plastic wrap and refrigerate, taking out every 10 minutes or to scrape down the sides with a rubber spatula, until the mixture is cool and thickened, but not set, 30 minutes to 1 hour. (Watch closely, because the exact timing depends on the refrigerator temperature and the chocolate brand.)
2Spread a 16-inch-long sheet of plastic wrap on a work surface. Spoon the chocolate
mixture along the end of the plastic closest to you, forming a 12-inch log. Starting at the closest side, roll up the chocolate in the plastic to make a rough cylinder. Tightly twist the ends of the plastic in opposite directions to enclose and form the chocolate into a salami shape. Gently roll the salami on the work area to smooth the salami surface. Place it on a small baking sheet. Refrigerate until firm, at least 2 hours or overnight.
3Unwrap the chocolate salami. Sift the confectioner’s sugar all over the salami to coat it. Tie the kitchen twine, if using, around the salami crosswise at 1-inch intervals. (If you want a very authentic appearance, look online for directions on how to do a “butcher’s knot” with a single long piece of kitchen twine.) The salami can be wrapped in plastic and refrigerated for up to 2 days.
4To serve, cut the chilled salami into thin slices. Let stand for a few minutes for it to lose its chill, and serve.
Note: If you have concerns about using raw egg, use an organic egg or look for pasteurized eggs at well-stocked natural food stores and supermarkets.