Peel potatoes and slice 1/16 of an inch thick (either with a mandoline or a with a knife). Place one single layer of potatoes in the gratin pan, add ¼ cup of the cheese and sprinkle 1/8 tsp of the garlic, repeat this process, layering potatoes, cheese and garlic until all 4 potatoes have been used.
Slowly pour the cream and milk mixture on top of the layered potatoes making sure it is well distributed in all the nooks and crannies.
Top potatoes with remaining ½ cup of cheese.
Bake uncovered for 1 hour 30 mins until a knife slides easily into potatoes and they are soft and tender. If cheese starts to brown too quickly cover with foil for the remaining duration of cooking time.
Allow to cool completely before refrigerating. Cover with foil and place in fridge.
To rewarm, heat covered for 30 mins in a 375 oven, remove foil and heat for another 10-15 mins more.