Wash the tomatillos well and cut into wedges about half inch thick.
In a wide frying pan, heat oil and sauté onions, garlic cloves, and panch phoron for about 2 minutes. Add 1/4 tsp salt, turmeric, red chili powder, and coriander powder and cook covered until the onions are soft (3-4 minutes).
Add tomatillos and sugar. Cover and cook 5 minutes.
Add shrimp plus 1/4 tsp salt and stir gently. Continue cooking (uncovered now to dry it up) until shrimp is cooked through and tomatillos have softened.
Finish with green chilies, cilantro, black nigella seeds, and ground panch phoron powder.