How to Make It
Place chicken and chicken stock in a programmable pressure multicooker (such as Instant Pot). (Times, instructions, and settings may vary according to cooker brand or model.) Cover cooker with lid, and lock in place. Turn steam release handle to SEALING position. Select MANUAL/PRESSURE COOK setting. Select HIGH pressure for 4 minutes (It will take 5 to 8 minutes for cooker to come up to pressure before cooking begins.) Carefully turn steam release handle to VENTING position, and let steam fully escape (float valve will drop). (This will take 1 to 2 minutes.) Remove lid from cooker. Transfer chicken to a large bowl, and shred with forks; set aside.
Select KEEP WARM setting on cooker. Add cream cheese to cooker, and whisk until completely melted. Whisk in sour cream until smooth. Stir in parsley, onion powder, garlic powder, dill, and salt. Transfer shredded chicken to cooker, and add Cheddar, pepper Jack, bacon, and scallions. Stir to combine. Divide chicken mixture evenly among buns (about 2/3 cup each), and serve immediately.