Peel the potatoes, unless the skins are very thin and you enjoy more texture in your potatoes. Cut them into quarters or slightly smaller.
Put them in a pot (Instant Pot is good) and add the stock.
Put on high pressure for 6 minutes in IP or boil for 15 minutes, or until potatoes are soft enough to insert a fork easily.
Take out the bay leaves and a some of the stock. Reserve the stock for mashing.
Mash the potatoes, adding back enough of the liquid so that the potatoes are not dry and are the right texture.
Add salt to taste.
Put the potatoes in a serving bowl and add a good sized chunk of butter.