Press the SAUTE button on your Instant Pot & set it to NORMAL. It automatically sets for 30 mins.
Add coconut oil to the pot, when the oil becomes hot throw in the mustard seeds & the dried chilies. Allow them to sizzle for a few seconds.
Next, add the chopped onion & sweat them off. it should take you about 2 mins. Add salt to catalyze the process.
Now, add the ginger garlic paste & saute until raw smell of the paste disappears. It should take you another 2 mins or so.
Throw in all the spices + the tomato puree. Mix & saute for 1 min.
Add the coconut milk & little water about 1/2 cup (add more if you like very thin gravy).
Cancel the SAUTE mode. Close the lid of the IP, seal the valve by moving it to the SEALING position.
Press the PRESSURE COOK button, set the timer for 2 mins & set it on HIGH.
After 2 mins when the IP starts to beep. Do a QPR (quick pressure release) & open the lid. The curry sauce is ready, it's time to add the fish.
Now, add the fish fillets. At this point if you feel that the gravy is not enough to hold all the fish fillets just add a little bit water or may be some more coconut milk diluted with water.
Close the lid of the IP. Seal the valve. Press the PRESSURE COOK button. Set the timer for 1 mins & set it to HIGH.
After 1 min when the IP begins to beep. Wait for NPR (natural pressure release) wait until the floating valve in your IP drops.
Open the lid carefully. You may garnish with cilantro & slit Indian green chilies if you want. Serve with rice. Enjoy!