Boil the potatoes for mashing. Meanwhile, sautee or sweat the vegetables. When the potatoes are done, drain them, then add in the vegetables, butter/oil, milk/stock/water, and mash with a hand-held potato masher. This is where the recipe gets its name; in Dutch, stamp means “to mash”, and a stamper is a “masher”. To “stamppot” is to mash the pot.