Heat the Instant Pot using the saute high function. Add the olive oil and allow it to heat for a minute.
Next, add the cabbage and cook, stirring occasionally, until it has softened, about 5 minutes.
Add the garlic and cook for an additional minute.
Next, add the potatoes, water, cream, 2 tablespoons of butter, salt, and pepper.
Attach the lid and ensure the valve is in the “sealing” position.
Set the Instant Pot to pressure cook on high manual for 7 minutes.
When the timer finishes, release the pressure manually by switching the valve to the “venting” position. Be careful the steam is very hot.
Add the remaining butter and mash the potatoes to your desired consistency. I like using an immersion blender to mash potatoes but you can also use a hand masher or stand mixer.
Season with additional salt and pepper if needed.
Serve hot.
Store any leftover potatoes in an airtight container in the refrigerator for up to two days.