Pound the garlic in a mortar and pestle to make a paste, and set aside. Place the onions, mint, cilantro, curry leaves, chilies, and yogurt into a blender and process until smooth. Transfer the mixture to a bowl, and add the reserved garlic paste and the rest of the marinade ingredients (chickpea flour, black pepper, cinnamon, ajwain, allspice, ginger, and lemon juice).

Place the shrimp in a shallow dish, and coat in the marinade. Cover with plastic wrap, and leave to marinate in the fridge for 30 minutes.

Preheat the grill to medium-high heat, then clean and oil the grill grates to prevent sticking. Have read a wire rack placed on top of plate or baking sheet.

Remove the shrimp from the marinade, brushing off the excess. Thread 2 to 3 shrimp on skewers. Drizzle with the vegetable oil and season with salt and freshly ground pepper.

Place the shrimp on the grill, sliding a piece of aluminum foil under the exposed part of the skewers to prevent burning. Turn over after 2 minutes, and cook until shrimp is tender and pink.

Transfer the shrimp to a wire rack to let the excess moisture drip off. Brush the shrimp with ghee and place back on the grill for 1 more minute for final char marks.