Mix together the beef, shallot, garlic, lemongrass, sugar and fish sauce in a bowl.
If using grape leaves, rinse, drain and pat them dry. Put about 2 teaspoons of filling in the center, slightly closer to the wider end. Fold the wide end over the filling, fold in the sides, and then roll up carefully, making sure the filling is completely and tightly enclosed. Repeat the process with the remaining leaves and beef mixture.
Depending on length of skewers, slide 3 to 5 beef rolls crosswise onto each skewer. Grill over a barbecue (make sure flames have subsided and coals are red, with white ashes) or on a well-oiled grill pan over medium-high heat, about 2 minutes per side. Serve with Nuoc Cham sauce for dipping.
Whisk together the sugar, water, fish sauce, and lime or lemon juice in a bowl, until the sugar is completely dissolved. Add the garlic, chile, and shallot if using, and let stand for 30 minutes before serving.
From "Authentic Vietnamese Cooking: Food from a Family Table" Simon & Schuster, 1999. important sauce in Vietnamese cooking, used as a dipping sauce with many dishes, including spring rolls, crepes, grilled meats and seafood. For a spicier sauce, mince rather than slice the chilies and garlic. Any leftover sauce can be refrigerated for up to 2 weeks.
From "Authentic Vietnamese Cooking: Food from a Family Table" Simon & Schuster, 1999.