1. Place potatoes and 1 1/2 teaspoons salt in a large stockpot. Add enough water to cover. Bring to a boil, reduce heat, and simmer until the potatoes are tender but not mushy when pierced with the tip of a knife, 15 to 20 minutes.

2. Drain potatoes, and transfer to an electric mixer fitted with the paddle attachment. If you prefer a lumpier consistency, you can mash them with a potato masher. Add 3/4 cup milk, the butter, garlic, and pepper. Mix on low speed to combine, then increase the speed to medium to mix thoroughly. Add more milk if the potatoes seem too thick. Taste, and season with salt as desired.