recipe adapted from here.
1 1/2 cups of heavy cream
2 tsp of kosher salt
3 cloves of garlic, minced
1 tbsp of butter
1 small shallot, diced
5 medium Yukon Gold or White potatoes
1 cup of grated Gruyere
1 /2 cup of grated Parmesan
1 tsp of fresh thyme
Preheat the oven to 325 F.
In a small saucepan add the cream, salt, and garlic. Bring to a simmer on low heat a cook for 5 minutes. This will allow the garlic flavor to infuse the cream. Remove from the heat and set to the side.
Thinly slice the potatoes to 1/8 inch thickness using a mandoline.
In a 12 inch cast iron pan, add the butter and shallots and fry on low heat for 5 minutes until the shallots have caramelized.
Arrange the sliced potatoes in a spiral pattern on top of the cooked shallots. Pour the cream mixture over top of the potatoes.
Cover the cast iron pan tightly with a piece of tin foil. Place the cast iron pan into the oven and bake for 1 hr and 15 minutes.
Remove the pan from the oven and turn the oven temperature to broil.
Cover the potatoes with the grated Gruyere and Parmesan cheeses. Sprinkle with the thyme. Place the cast iron pan into the oven and broil for 5 minutes until the cheese is crispy and bubbling.
Remove from the oven and serve warm.
It can be stored in the fridge and reheated the next day.