Preheat oven to 400 degrees then butter or coat a 9" pie dish with cooking spray. Peel potatoes (if desired) then cut into equal-sized chunks. Place potatoes and sliced garlic in a large pot then add enough cool water to cover by at least 1".
Set pot over high heat then bring to a full boil. Reduce heat to medium-low, add a few heavy pinches of salt then simmer until the potatoes are completely tender. The garlic will soften and mellow in flavor as the potatoes cook.
Drain potatoes thoroughly then return to pot and place back on heat, stirring constantly. Cook just long enough to remove the excess moisture remaining on the potatoes. When steam stops rising from the pot, remove from heat then add butter and milk. Mash the potatoes and garlic to the desired consistency, season to taste with salt and pepper.
Transfer to prepared pie dish. Sprinkle the top of the potatoes with Parmesan cheese then place mozzarella slices over the top. Sprinkle basil, oregano, salt and pepper on top of the mozzarella then bake 30 minutes or until the cheese is golden brown and bubbly. Let the pie sit for a few minutes before serving—it’ll be hot! Enjoy!
Fresh mozzarella usually requires a bit of salt, which is why we recommend sprinkling salt on top of the pie after you’ve seasoned the potatoes.