Sear Chicken: Set the Instant Pot on SAUTE function & set it on HIGH heat. Add 2 tbsp olive oil, when the oil is hot gently release the chicken drumsticks and sear both sides until golden. Set them aside.
Saute aromatics & Pepper: Use the same settings and the same pot. Add the rest of the 2 tbsp oil. Saute the onion and garlic until the onion becomes limp. Add salt to quicken the process. Than, add the green bell pepper & saute until the pepper begins to turn soft.
Saute Seasonings: CANCEL the SAUTE function. Than, add all the seasonings - ground black pepper, cayenne pepper & paprika. Stir immediately and saute for just 30 seconds. The residual heat should be enough to slightly saute the seasonings. NOTE: Paprika burn quickly, so DO NOT saute more than 30 secs. It'll make the sauce bitter!
De-glaze pot: Now, pour chicken stock and de-glaze the pot very well scraping the bottom & the sides of the pot with the help of a spatula. There should not be any food particles stuck at the bottom of the pot. This will prevent the BURN error. DO NOT rush this step!
Pressure Cook: Transfer back the seared chicken into the pot. Coat the chicken with the sauce. Close the lid of the pot, seal the valve and PRESSURE COOK on HIGH for 5 mins. Once, the pressure cooking cycle is over the Instant Pot will begin to beep, perform a natural pressure release (NPR) for 5 mins and than release the rest of the pressure manually by moving the valve from the sealing to the venting position. When the floating pin drops open the lid carefully.
Stabilize cold sour cream: Now, fish out the cooked chicken, set them aside. Stabilize the sour cream by adding 2-3 ladles of the hot sauce from the pot into the cream. Also, add the thickener (flour or cornstarch) and whisk them well until a smooth mixture forms. There should not be any flour lumps.
Thicken Sauce: Now, add this stabilize sour cream into the hot sauce in the pot and stir well to mix. Hit back the SAUTE function and set the heat to LOW. Simmer the sauce stirring frequently until it thickens and reaches your preferred consistency.
Serve: Transfer back the cooked chicken into the pot. Coat them well with sauce and simmer for just 1 minute. Garnish with chopped parsley and serve hot over. Enjoy!