Season chicken thighs with salt and pepper. Add vegetable oil to Instant Pot and select "Saute". When hot, add chicken and cook for a 2-3 minutes per side each side, until well browned. You don't want to overcrowd the pot, so you may need to do this in batches.
Remove chicken to cutting board and cut into bite-sized pieces.
Add onion, serrano, tomato paste, garam masala, tumeric, smoked paprika, cumin and sugar to Instant Pot. Cook 3-4 minutes, until onion is soft and slightly browned at the edges.
Stir in garlic and ginger and cook another 30 seconds or so. Add 1/4 cup chicken broth to scrape up any browned bits at the bottom of the pot. Browned bits on the bottom can result in a BURN notice from the Instant Pot.
Return chicken pieces to the pot, along with tomato sauce and remaining 1/4 cup chicken broth. Stir slightly.
Close lid securely and make sure the valve is set to "sealing". Select "Manual" or "Pressure Cook" and adjust the +/- button until it reads 8 minutes.
When finished cooking, carefully turn the valve to "venting" for a quick pressure release. When the steam has all escaped, and the pin has dropped, remove the lid.
Use a slotted spoon to remove chicken to a plate and cover to keep warm. Select "Saute".
Add yogurt to a small mixing bowl. Ladle about 1/2 cup of the sauce from the Instant Pot and slowly pour it to the yogurt, while whisking quickly. This tempers the yogurt so it doesn't curdle.
Stir the yogurt mixture into the Instant Pot and let simmer for several minutes, until thickened to your liking.
Return chicken to the pot, along with minced cilantro. Stir and serve hot.