Preheat your oven to 425 degrees
Generously butter the interior of a 3 quart baking dish and set aside for now
Combine 3 cups of heavy cream with 2 cloves of minced garlic, 1/2 teaspoons of nutmeg and 2 sprigs of fresh thyme in a saucepan and place over medium heat
Bring the cream just to a simmer and turn the heat off
Very thinly slice 3 pounds of potatoes and shred 8 ounces of gruyère
Add a ladle of the cream into your baking dish and shingle a layer of potatoes
Lightly salt and pepper the potatoes, add a ladle of cream and top with a thin layer of shredded Gruyère
Repeat until all of the ingredients are assembled
Cover the baking dish with foil and bake in a 425 degree oven for 40 minutes then reduce the ovens temperature to 350 degrees and bake for another 30 minutes
Remove the foil and bake for another 30 minutes or until the potatoes are tender and the top layer is golden brown
Allow the potatoes to cool for 10-15 minutes before slicing
Garnish with fresh thyme and additional shredded Gruyère