Finely slice the potatoes using a mandoline and set aside in water until ready to use. Combine the cream, milk, nutmeg, garlic and a pinch of salt and pepper in a large saucepan and bring to the boil. Once boiling, remove from the heat and set aside. Strain the water off the potatoes and layer inside a small oven dish lined with parchment paper, sprinkling gruyere cheese between each layer and being sure to overlap each layer as you go. Preheat the oven to 350 degrees. Pour enough of the cream mixture over the potatoes to cover and bake in the oven for 45 minutes or until slightly golden on top and tender through the middle. Remove from the oven and allow to cool. Weigh down with butter, cheese or any other heavy square object and set aside in the fridge to press for up to 12 hours. Reheat the potato dauphinoise in the oven set to 350 degrees for 15 minutes. Divide into portions and serve immediately as a side dish.