Fill medium pot with water, then add 1 tablespoon salt and stir to incorporate. Once incorporated, add 2 pounds russet potatoes and place pot on stovetop over medium-high heat.
Once water begins to boil rapidly, set timer and boil potatoes 5 to 8 minutes, or until potatoes can be easily pierced with tines of fork.
While potatoes boil, add 3 tablespoons butter and ½ cup whole milk to small saucepan. Place saucepan on stovetop over medium heat. Heat mixture, whisking occasionally, until butter is completely melted.
When potatoes are fork-tender, carefully drain all liquid from pot, then place pot on cool stovetop burner.
Use potato masher or fork to mash potatoes to desired consistency, then gradually stir in butter-milk mixture, making sure to incorporate all liquid into mashed potatoes.
Once combined, season potatoes with ½ teaspoon garlic powder, salt, and freshly cracked black pepper. Stir well to incorporate, then taste and adjust seasonings as needed. Set potatoes aside until ready to serve.