Marinate fish steaks with half turmeric powder and salt for 10 minutes.
Heat mustard oil in a pan, light-fry fish steaks and potato batons until golden; set aside.
Temper cumin seeds in the oil, add ginger paste, remaining turmeric, and salt.
Add water and bring broth to a boil.
Add fried fish and potatoes, cover, and simmer for 10 minutes until potatoes are soft.