In a bowl, combine the beef with green onion, fish sauce, salt, pepper, and curry powder. Add the soda water and mix in enough to yield a soft mixture. The soda water hydrates and keep the filling moist during cooking. Cover and set aside to marinate while you prepare the leaves.

If you haven’t, use scissors or your fingers to detach the leaves from their center stems. Make sure to keep the leaf stem attached to the leaf. You’ll need it later for creating the rolls.

To make the rolls, put a leaf on your work surface, matted side up. Take a bit of meat (about 2 tablespoons) and use your hand to shape it into a small sausage of sorts. Place the meat on the leaf, about a third of the way below the pointy tip. The length of the sausage doesn’t need to span the full width of the leaf because the leaf shrivels during cooking. Roll up the meat in the leaf and use the little stem to seal it up. The roll will keep its shape. Place the finished roll on a foil-lined baking sheet. Repeat with the remaining leaves until all the beef is used. Rub a bit of oil on each roll when all are done.

To cook, position an oven rack on the top third of the oven and preheat to broil. Slip the baking sheet into the oven and broil for 6 to 8 minutes, turning them frequently to cook evenly and prevent too much charring of the leaf. The cooked rolls will feel firm, look a bit shriveled, and be slightly charred at the edges.

Instead of broiling, grill outdoors over a medium charcoal fire (you can hold your hand over the rack for only 4 to 5 seconds) or heat a gas grill to medium. Grill the rolls, with the top open most of the time so you may constantly monitor their progress and move them around to avoid burning the leaves. (The heat will go to about medium-low because you'll have the lid open.)

Transfer to a plate and serve with the dipping sauce, pickle, and lettuce. Invite guests to encase a beef roll in lettuce, add some pickle, and dip in sauce.