Peel and quarter the potatoes, then place them in a large pot of cold salted water.
If desired, add the garlic cloves to the pot. Bring the water to a boil and cook the potatoes uncovered for about 15 minutes or until they are fork-tender. Drain the potatoes well.
While the potatoes are draining, gently heat the milk on the stovetop or in the microwave until it is warm but not boiling.
Return the drained potatoes to the pot. Add the melted butter and start mashing the potatoes. Gradually pour in the warm milk, continuing to mash until you reach the desired creamy consistency.