Place a steamer basket in the inner pot and pour in one cup of water.
Place potatoes in the basket and sprinkle with ¼ teaspoon of salt.
Cover and lock the lid in place. Place the vent to the sealing position and set to manual on high pressure for 9 minutes. When the cook time is done, quick release the pressure and turn off the heat (press cancel).
Carefully drain the potatoes and return back to the pot. Add buttermilk, olive oil and remaining ¼ teaspoon of salt. Using a potato masher, mash until potatoes are smooth and creamy. Serve warm.