Place prepared potatoes into the Instant Pot. Pour in the chicken broth to cover them (about 4-5 cups). Secure the lid into place, lock it, and position the valve to sealing. Cook the potatoes on high pressure for 8 minutes. When the potatoes are ready, do a quick release.
Remove the inner pot from the pressure cooker. Drain the potatoes, then return them to the pot. Add salt and pepper to taste, then transfer the herb and garlic butter, milk, and Greek yogurt to the Instant Pot. Mash the potatoes with a potato masher until smooth. Give everything a good stir. Taste, and adjust the salt and pepper if needed.
Transfer the potatoes to a serving bow, top with a pat or two of butter, and garnish with chopped fresh parsley or chives.