12 Roast the garlic: Preheat the oven to 375°F. Slice the top off the garlic head, drizzle lightly with olive oil, wrap in foil, and roast for 1 hour, until soft and deeply golden. Let cool and reduce the oven to 350°F.
1 Make the garlic cream: Squeeze out the cooled roasted garlic cloves into a blender with the milk. Blend until smooth. Transfer to a saucepan and add the heavy cream, salt, white pepper, allspice, smoked paprika, and herbs de Provence. Warm over low heat until steamy but not boiling. Set aside.
3 Prep the potatoes: Using a mandoline, thinly slice the potatoes.
4 Prepare the pan: Butter an 8x8-inch baking dish, then line it with two overlapping sheets of parchment, leaving overhang on the sides so you can lift the slab out later.
14 Combine the cheese: Mix together the gruyere and Parmigiano cheeses. Cover and refrigerate the other half for topping later. The other half you will use in the next step.
13 Layer the potatoes: Add a thin ladleful of the garlic cream to the bottom of the pan. Then we layer. The order is a thin layer of potatoes → garlic cream → potatoes → garlic cream → VERY thin layer of the cheese mix → potatoes. Repeat this until you have 8 layers of potatoes. Your top layer should be potatoes and then cream.
6 Bake to set: Cover the dish tightly with foil and bake at 350°F for 75 minutes.
7 Press and chill: Let the dish cool. Place a sheet of parchment over the top, then the other 8x8-inch baking dish on top of the potatoes and press down, and add heavy cans to weigh it down. Refrigerate for at least 8 hours or overnight so the layers set and you can cut clean stacks.
15 8 Hours - Overnight Later: After it has chilled in the fridge, move it to the freezer for about 30 minutes while you preheat your oven to 425°F.
8 Cut into Stacks: Use the parchment overhang to lift the chilled potato slab out of the pan. Trim the edges, then cut into neat squares or rectangles to form stacks.
9 Top with Cheese and Bake: Arrange the stacks on a parchment-lined baking sheet. Top each stack with the remaining gruyere and Parmigiano mixture. Bake for 35-45 minutes until the top is deeply golden.
11 Top and Serve: Top with fresh chopped chives, crème fraîche and caviar! Enjoy!
