Wash and cut the kathal into square pieces and boil it for 2 minutes with salt and turmeric powder. (If using the canned ones, drain the water and clean with fresh water.)
Sprinkle some salt and ½ turmeric powder over it and keep aside.
Cut potato the same size.
Heat a kadai, and add oil. After heating, add whole garam masala, whole jeera and bay leaves.
Add potato and fry till golden brown, and remove from kadai.
Add onion, ginger, and garlic paste and fry for 5 min.
Add all other masalas and both tomatoes and curd and fry them till oil separates (except the garam masala powder).
Add kathal and potatoes to it and mix well. Cover and cook for 10 minutes on low flame.
When oil separates, add water and bring to boil.
Again, cover for 5 minutes and add garam masala powder and remove from heat.
Serve hot.