How to Make It
In a large, shallow dish, whisk the sour cream with the garlic, cumin seeds, garam masala, peppercorns, ground cumin, ginger and turmeric. Add the shrimp and coat thoroughly with the marinade. Cover and refrigerate for 3 hours.
Light a grill. Remove the shrimp from the marinade and thread onto skewers; season with salt. Oil the grates and grill over high heat until almost cooked through, 2 minutes per side. Brush the shrimp with the butter and grill until glazed and just cooked through. Sprinkle the shrimp with the chat masala and serve with lime wedges.
Chat masala is a spicy, tangy Indian spice blend. It is available at Indian markets and at kalustyans.com.