Place the potatoes, water, and 2 teaspoons of salt in the bowl of the Instant Pot.

Secure the lid on the Instant Pot and Pressure Cook on High for 12 minutes. Quick release the pressure, reserve 3/4 cup of the potato cooking water, and drain.

Return the potatoes to the pot and add the garlic, olive oil, butter, and the remaining 2 teaspoons sea salt. Use a potato masher to mash well. Add the reserved cooking water, 1/4 cup at a time, and use a rubber spatula to fold and mash the potatoes until creamy. Stir in the remaining cooking water as needed to reach your desired consistency.

Season with fresh black pepper and garnish with chives.