Chop the entire white portion and a small amount of the green portion of the leek into rounds. Don't worry about breaking the pieces apart, this will happen naturally as they saute. Finely dice the onion. Peel and chop the potatoes into large chunks. Crumble up the cooked bacon.
Plug in the Instant Pot and press the Saute button. Pour in the oil and allow to heat for about a minute. The Saute function heats the pot very quickly so make sure you have your leek and onion ready to go before you turn it on. Add them in and saute for about 5 minutes until the leeks are tender and the onion is translucent.
Turn the Instant Pot off.
Add the potatoes, broth, bacon, salt, and pepper to the pot and stir to combine.
Put the lid on the pot and close the vent. Press Manual and set the timer for 12 minutes.
Allow the timer to continue for an additional 10 minutes after the cook time is complete and then turn the steam release handle to let the rest of the steam release.
Scoop out two cups of potatoes and place in a blender. Add the coconut milk (or regular milk) and blend until smooth.
Pour the potato and coconut milk mixture back into the pot. Mash up large chunks of potato and stir to combine.
Garnish with green onions and serve with a slice of warm, homemade bread.