How to Make It
In a mortar, pound the garlic, ginger and salt to a paste; alternatively, puree in a mini-processor. Add the lemon juice and 2 tablespoons of the yogurt. Transfer the mixture to a large bowl. Whisk in the remaining yogurt along with the egg, chickpea flour, cayenne, turmeric, cumin, garam masala and white pepper. Stir in the shrimp and marinate for 2 hours.
Light a grill. Thread the shrimp onto skewers. To suspend the shrimp 2 to 3 inches above the grill, place rocks or bunched-up foil on either end of the grill. When the fire is hot, rest the skewers on the rocks and cover the grill. Cook for about 5 minutes, or until the marinade has formed a firm, crusty coating on the bottom of the shrimp. Baste the shrimp with the butter and turn the skewers. Cover and grill the shrimp until just cooked through, about 4 minutes longer. Transfer the shrimp to plates and serve at once, with lemon wedges.