Heat the vegetable oil in a large stock pot over medium heat. Add the lobster bodies and brown on all sides. Add the crab paste, ginger, galangal, and lemongrass. Continue to cook. Once the vegetables start to soften, add the kefir lime leaf. Add the chicken stock and coconut milk, and bring to a simmer. Gently simmer for 45 minutes. Strain the broth and chill completely. Add the chilled broth to a blender. Add the Chinese chives and the fish sauce. Blend until smooth.