Soak skewers in cold water for at least 20 minutes (this prevents burning). In a blender, combine cream, onion, garlic, curry powder, cumin, cayenne and salt; blend until smooth. Transfer to a bowl and add chicken and beef strips; toss to coat. Cover and marinate at room temperature 15 minutes.
Make dipping sauce: In a blender, combine ingredients and blend until smooth. Transfer to a small bowl. (Sauce can be prepared up to 2 days ahead of time, cover and refrigerate.)
Heat broiler. Thread chicken and beef strips onto the skewers without crowding. Place on an oiled rack in a broiler pan and broil until cooked through, turning once, about 5 minutes. Serve with the dipping sauce.
