Place the potatoes in a medium saucepan, cover them with cold water and add enough salt so that your water tastes like the sea; it's imperative that your water be fairly salty!
Cook the potatoes over high heat until the water comes to a boil, then lower the heat to a high simmer, cover and continue cooking until the potatoes are super tender and pretty much fall apart when you pierce them with a fork, about 20 minutes.
In a small pot, bring the milk to a low simmer, then kill the heat and set aside.
When the potatoes are cooked, drain them and give them a minute or two to dry out in the colander, then return them to the pot.
Add a little bit more than half of the warm milk, the vegan butter, nutritional yeast and garlic and mash with a potato masher until all the ingredients are well combined and the potatoes are reduced to a rustic mash.
Switch to an electric mixer and whip the potatoes, starting on low and progressively moving on to high speed; stop to add more warm milk as needed, beating well between each addition, until the potatoes are completely reduced to a smooth puree and the desired consistency is achieved.
Adjust seasoning by adding more salt if needed and a few shakes of ground white pepper if desired, then give the potatoes a final beating and serve without delay.