Peel and cut the russet potatoes into even chunks, about 1-inch thick for uniform cooking.
Place the cut potatoes in a large pot. Fill the pot with water until the potatoes are covered by about an inch.
Add 1 teaspoon of salt to the water and bring it to a boil over medium-high heat.
Once boiling, reduce the heat to medium and cook the potatoes for about 15-20 minutes, or until they are fork-tender.
Drain the cooked potatoes in a colander and return them to the pot.
Add the unsalted butter to the hot potatoes and let it melt for a minute.
Gradually pour in the whole milk while mashing the potatoes with a potato masher or using an electric mixer, until you reach your desired creaminess.
Season with additional salt and black pepper to taste, mixing well to combine.
Serve the mashed potatoes warm in a serving bowl, garnished with fresh chives or parsley if desired.