Select sauté on the instant pot and adjust to normal.
Add oil to the pot.
When the oil is hot add the cumin seeds.
When the cumin seeds splutter add the serrano pepper, fenugreek leaves and spinach.
Stir and sauté for a minute.
Add the ground coriander, ground cumin, black pepper, red chili powder, salt, sugar and water.
Stir and sauté for 30 seconds.
Add the mushrooms and corn. Stir well. Make sure nothing is stuck to the bottom of the pot and scrape the bottom of the pot well.
Secure the lid on the pot and close the pressure-release valve.
Select manual and cook at high pressure for 7 minutes.
When cooking is complete, use quick pressure release to depressurize.
Open the lid.
Select sauté and add the whisked yogurt slowly (one spoon at a time) to the pot mixing it continuously.
Then add the half and half and stir.
Add dried fenugreek leaves and stir. This whole sauté process with these three steps should take about a minute. Stir.
Transfer the cooked dish in a serving bowl.