Push saute on the Instant Pot and add the 2 Tbsp butter and cabbage/kale/greens.
Saute for 2-3 minutes or until wilted.
Push OFF on the Instant Pot and dump in the potatoes, along with 1/2 C. water.
Push high (manual) and set the timer for 4 minutes.
At the completion of the 4 minutes, release the pressure (quick release) and lift the lid.
Mash the potatoes with a masher right in the pot, mixing them up with the greens. Add the milk and salt/pepper and combine together until well blended.
Serve hot in a bowl with a knob of butter (3 Tbsp) in the center.