Heat 1 tablespoon of canola oil in the same pan you cooked the rice (to keep it one pot). Add the curry leaves, cumin seeds, mustard seeds, red chili pods, cloves, cardamom and black peppercorns (optional). Fry for 1 minute. Then add onions and asparagus. Fry for 2-3 minutes.
Add the ground spices (coriander, turmeric, curry powder) and salt. Fry for 30-45 seconds. Then add the buttermilk and shrimp.
When shrimp starts to turn pink (but is not fully cooked) turn off stove. Taste for seasoning.
Butter a baking dish and layer some of the parboiled rice on the bottom. Then layer some of the shrimp and asparagus. Make sure you get some gravy on top of the rice. Layer with rice and shrimp and finish off with a rice on top. Pour gravy from the curry over the rice.
Preheat oven to 350 degrees. Place a tight fitting lid or tin foil over the baking dish to trap all the steam. Cook in the oven for 35 minutes. Once cooked, allow the dish to sit covered for additional 10 minutes before serving. Enjoy.