Peel potatoes then cut into 1" cubes. Be sure to keep the size of the potatoes as uniform as possible so they cook evenly. Place potatoes and salt in a large pot and cover with at least 1" of water. Bring water to boil over high heat then reduce to medium-low, gently boiling the potatoes for about 20–25 minutes or until they are fork tender.

While the potatoes boil, place butter in small saucepan then melt over medium heat. Add minced or roasted garlic to melted butter and let cook for 30 seconds then remove from heat.

When potatoes are tender, drain thoroughly then return them to pot. Place pot back on the heat, stirring constantly, until steam and excess moisture has cooked off the potatoes—this takes about 15–20 seconds.

Transfer potatoes to a large mixing bowl or the bowl of a stand mixer fitted with the whisk attachment. Beat potatoes for a few seconds to begin breaking them up then add butter and beat until nearly smooth.

Add about ½ cup of the half-and-half or milk then whip potatoes until light and fluffy. Test the potatoes for salt and season if needed. Add additional milk as needed to achieve the desired consistency then serve immediately.