preparationSpray the bottom and sides of a deep rectangular baking dish with non stick spray.
Preheat the oven at 375F
Using your fingers rub the bottom of the baking dish with the butter. Line the baking dish with the sliced potatoes slightly overlapping. Sprinkle with salt and pepper, and some of the gruyere cheese and some of the parmigiano reggiano cheese. Repeat until the the baking sheet is full, and on the top layer wait to put the cheeses.
Season cream with the salt, pepper, thym, garlic and nutmeg. Pour the mixture over the potatoes. Now top with the remainder of the cheese.
Cover the dish with alluminimn paper and bake for approximately 75 minutes or until the potatoes are cooked through.
Remove the allumnimum paper for the last 20 minutes to brown the top.
Allow to rest for 15 minutes before serving.