Cut the potatoes. Peel the potatoes if desired, or leave the skins intact. Cut them into evenly sized chunks about 1 inch thick and place them in a large stockpot filled with cold water.
Boil the potatoes. Make sure the potatoes are covered by approximately 1 inch of cold water. Add the minced garlic and 1 tablespoon sea salt. Place over high heat and bring to a boil. Reduce the heat to medium-high, or as needed to maintain the boil, and cook for about 10–12 minutes. The potatoes are ready when a knife slides into the center easily with almost no resistance. Drain thoroughly.
Prepare the butter and milk mixture. While the potatoes cook, combine the butter, milk, and an additional 2 teaspoons sea salt. Warm them in a small saucepan or microwave just until the butter melts. Do not allow the milk to boil. Set aside.
Pan-dry the potatoes. Immediately return the drained potatoes to the hot stockpot. Put the pot back on the burner and reduce the heat to low. Wearing oven mitts, hold the pot handles and gently shake the pot over the burner for about 1 minute to help remove remaining moisture from the potatoes. Take the pot off the heat and place it on a flat, heatproof surface.
Mash the potatoes. Using your preferred potato masher, mash the potatoes until they reach your desired consistency.
Combine. Pour half of the melted butter mixture over the mashed potatoes. Using a wooden spoon or spatula, gently fold until the liquid has been absorbed. Fold in the remaining butter mixture, followed by the cream cheese. Mix each addition only until combined to avoid overworking the potatoes. If necessary, add additional warm milk until the potatoes reach your preferred consistency.
Season. Taste and add extra salt if needed.
Serve. Serve the mashed potatoes warm with gravy or your choice of toppings.