Cheesy Potato and Mushroom Gratin

• 3 lbs Yukon gold potatoes, rinsed and sliced 1/16” thick
• 2 cups shiitake mushrooms, thinly sliced
• 1 Tbsp fresh thyme
• 1 Tbsp olive oil
• 1 1/2 cups heavy cream
• 3 garlic cloves
• 1 small shallot, finely chopped
• 1/2 teaspoon nutmeg (fresh grated is best)
• 1 tsp salt
• 1/2 tsp pepper
• 3/4 cups parmesan cheese, freshly grated
• 3/4 cups fontina, freshly grated

Preheat oven to 375°F. Slice the Yukon potatoes 1/16” thick using a Mandoline slicer and set aside. Heat olive oil in a medium skillet over medium- high heat. Add sliced mushrooms, thyme, and a pinch of salt and pepper and cook until soft. Set aside to cool.

In a large bowl, whisk cream with shallot, garlic, nutmeg, salt and pepper. Freshly grate the cheeses and combine in a small bowl. Add 1 cup of the cheese mixture to the cream and stir. Add the sliced potatoes and mix gently to coat them. Butter a medium copper roaster and arrange half of the potatoes in an even layer on the bottom of the pan. Add the cooked mushrooms evenly over the potatoes. Layer the remaining potato slices on top until the pan is filled. Cover the dish with foil and bake for 1 hour and 30 minutes. Sprinkle the remaining cheese and a few fresh thyme sprigs on top. Bake uncovered for another 15 minutes, or until the cheese has fully melted and the potatoes are tender. Let cool for 15 minutes before serving.