Wash, peel, and slice the parsnips into 1-2" chunks. Add the parsnips to the instant pot with the water, salt, and garlic cloves.
Place the lid on the Instant Pot and set the valve to seal. Using the manual setting, cook on high pressure for 10 minutes.
When the timer goes off, carefully perform a quick pressure release. Drain the water/vegetable broth from the parsnips.
Add the parmesan cheese, heavy whipping cream, fresh herbs, butter, salt, pepper, and mash until smooth using a potato masher or hand mixer. (For vegan option: use nutritional yeast and olive oil instead of cheese and whipping cream.)
Top with fresh parsley or chives and butter (optional). Enjoy!