Place wok/kadai on flame
Keep aside 1/2 cup of water
Add 1 tsp mustard oil (can use any other cooking oil as well)
Heat the oil well else it will start foaming
Once the oil is hot, add turmeric Powder
Mix turmeric powder with the mustard oil
Add a little bit of water from the half cup of water we'd kept aside
Lower the flame
Now add 4 tsp coriander Powder, red chilli powder, kashmiri chilli powder and garlic paste
Now add the main ingredient - Yellow Mustard Seeds
Add the tomato paste and chopped tomato
Add salt
Add the remaining ½ cup of water
Now stir and cook the mixture
Once it boils, lower the flame and cover and cook it for 5 minutes - this will help to cook the tomatoes
Once the tomatoes have softened, cook the mixture for 10-12 minutes till it dries up - cook on medium flame, if needed can increase to high
Once it dries up, you know the masala is ready
Now add 1½ cups of water
Increase flame to high and bring it to a boil
Once it's boiling, lower the flame to medium and cook for 5 mins
Now add fish to the gravy and adjust the flame to low
Make sure the fish is covered with gravy (The fish is almost cooked anyway)
We will cover and cook this for another 2 mins
Sarson fish is now ready!Serve and garnish with 1 tsp Kasuri Methi