Using a sharp knife, chop the scrubbed and peeled potatoes into 1” cubes.
Fill a large saucepan or Dutch oven with water, then add the potatoes to the water. Place the garlic cloves in the water, as well.
Season the water with a teaspoon of salt.
On the stovetop, heat the water and potatoes over high heat and bring to a boil. Cook until the potatoes are fork tender, about 20 minutes.
Drain the potatoes, and place back in the saucepan.
Measure out the butter, milk and 1 cup of parmesan cheese on top of the potatoes.
Using a hand mixer on a low speed, slowly blend the ingredients together until smooth and creamy.
Season the potatoes with salt and pepper.
Preheat the oven to 350°F. Spray a 9'' x 13'' baking dish with nonstick cooking spray, and set aside.
Transfer the mashed potatoes into the prepared baking dish. Sprinkle the additional ¾ cup cheese on top of the casserole.
When the oven is preheated, transfer the casserole to the oven.
Bake for 25 minutes, then turn up the heat to 425°F. Bake for an additional 15 minutes, or until the cheese has browned.
Remove from the oven, and let cool slightly.
Serve warm, and enjoy!