Preheat the oven to 425°F. Wash, peel, and slice the potatoes to 1/8 inch slices. Use a food processor to quickly slice the potatoes.
Slather on a thick layer of butter on a medium sized baking dish. Layer the slices of potatoes in a thin layer. The potatoes may over lap a little.
Pour about 1/3 of the cream over the potatoes. Sprinkle 1/3 of the parmesan cheese over the potatoes. Sprinkle a little garlic, thyme, salt and pepper over the cheese.
Start the second layer of potatoes over the first layer. Add the milk, cheese, garlic, thyme, salt and pepper again.
Repeat for a third layer. Pour the remaining milk, cheese, garlic, thyme, salt and pepper over the potatoes. Add the mozzarella cheese on top. Place tin foil over the pan and place in the oven to cook for 45-60 minutes.
At about 40 minutes of cooking, remove the tin foil and allow the dish to cook for 5-10 more minutes. This will help the cheese brown. Remove from the oven when the cheese is browned and crispy. Mangia!