Clean the mussels well and allow it to drain.
Mix the ingredients for marinade: slit cocum, ground green chillies, ginger, curry leaves, turmeric powder and required salt. Apply the marinade on the mussels and keep aside for 30 minutes.
Take a vessel and put the marinated mussels and sufficient water. Boil and cook in low heat until the mussels are cooked and water evaporates completely.
Heat oil in a pan and splutter mustard seeds. Add chopped onions, slit green chillies, ginger, garlic and curry leaves. Saute well until the onion becomes golden in color.
Add chilly powder, coriander powder and garam masala powder and saute for a few minutes.
Stir in cooked mussels and add little water. Keep stirring until the mussels are well fried.
Mussel fry in malabar style is ready and serve hot.