Step 1: Place the garlic, scallion white, ginger, lemon zest, soy sauce, sugar, sesame oil, and sherry in a blender and purée until smooth. Or you can make the marinade in a food processor: Place the garlic, scallion white, ginger, lemon zest, and sugar in the processor bowl and process to make a fine paste. Add the soy sauce, sesame oil, and sherry and process to mix.

Step 2: Using a very sharp knife, cut each steak on the diagonal into about 36 thin slices (about ⅛ inch thick). Weave each strip of meat like a ribbon onto a skewer. The meat will bunch up as it goes on the skewer; gently spread it out with your fingers.

Step 3: Arrange 12 of the kebabs in a single layer in a nonreactive baking dish. Pour one third of the marinade over the kebabs in the baking dish. Turn the kebabs to coat both sides with the marinade. Arrange 12 more kebabs on top of the first layer, pour half of the remaining marinade over these, and turn this layer to coat evenly. Arrange the remaining kebabs on top of the second layer, pour the remaining marinade over these, and turn to coat evenly. Cover the kebabs with plastic wrap and let them marinate in the refrigerator for 1 to 2 hours.

Step 4: Set up the grill for direct grilling and preheat to high.

Step 5: When ready to cook, brush and oil the grill grate. Tear off a piece of heavy-duty aluminum foil that is roughly as long as the grill is wide. Fold the piece of aluminum foil in half lengthwise. Place the folded aluminum foil flat on the grate at the edge closest to you. Arrange the kebabs on the grate so that they are over the fire but the exposed ends of the skewers are on the foil shield to keep them from burning. Depending upon the size of the grill, you may need to cook the kebabs in batches. Grill the kebabs until nicely browned, 1 to 2 minutes per side for medium. Transfer the grilled kebabs to a platter and sprinkle the scallion greens over them.