2/3 cup coarsely chopped fresh cilantro, plus sprigs for garnish
1 tablespoon chopped fresh mint
2 large lemons, each cut into 8 wedges
Toast peppercorns and coriander in a small skillet over medium heat, swirling pan, until spices are fragrant, about 2 minutes. Transfer to a spice grinder, and process until finely ground.
Heat oil in a medium skillet over medium-high heat. Add scallions, ginger, and 2 teaspoons salt. Cook, stirring occasionally, until scallions are tender, about 3 minutes. Stir in ground spices, and cook for 30 seconds. Stir in turmeric. Transfer scallion mixture to a large bowl, and let cool, about 20 minutes.
Add beef, cilantro, and mint to scallion mixture, and gently mix. Refrigerate for 30 minutes.
Divide meat mixture into 16 pieces, then form each piece into a log, 1 1/2 inches thick. Slide a skewer lengthwise through center of each log. Place a lemon wedge on end of each skewer. Place skewers on a baking sheet, and refrigerate for 30 minutes.
Preheat grill to medium-high. Season kebabs with salt and pepper. Arrange on grill, and cook, undisturbed, for 3 minutes. Carefully turn skewers a third of the way, and cook for 2 minutes. Turn skewers a third of the way again, and cook for 2 minutes. Transfer skewers to a plate, garnish with cilantro, and serve immediately.