5lbsrusset potatoespeeled and cut into 2-inch pieces
2tspkosher saltplus more for boiling potatoes
¾cupwhole milkheated, plus more as needed
Place potatoes in a large pot, cover with cold water by 2 inches and bring to a boil; add salt Simmer until fork-tender but not falling apart, about 30 min; drain
Transfer potatoes to a large mixer bowl and, using whisk attachment, beat on medium speed until finely crumbled. Add milk, butter and 2 tsp salt; beat until just smooth, adding more milk as need for a light, creamy texture.
I love using russet potatoes for fluffy mashers. Waxy potatoes are delicious, but they don't have the same fluffy texture. They are smooth and rich, but a very different situation.