Place cilantro leaves, lemon juice, ginger, garlic, jalapeños, salt, curry powder, cayenne and 1/2 cup water into a blender. Blend until smooth.
Coat bowl of a slow cooker with nonstick cooking spray. Add lamb, onion and cilantro mixture; stir to combine. Cover and cook on LOW for 7 1/2 hours. Stir in chickpeas and coconut milk; cook 30 minutes more.
Serve curry over cooked basmati rice.