2 cups heavy cream
Kosher salt and pepper
2½ pounds Russet potatoes (about 4-5 large)
1-1 ¼ cups grated Parmesan cheese
1-2 cups broccoli florets and pieces, chopped finely (trimmed from the grilled broccoli recipe – link to Dish 3)
2 ounces prosciutto, very thinly sliced
Heat the oven to broil.
Peel the potatoes and very thinly slice them on a mandolin to the thickness of a quarter.Place the cream in a large bowl. Season it with salt and pepper, about 1 teaspoon kosher salt and 1/8 teaspoon ground pepper. Immediately place the slices in the bowl of seasoned cream so they don’t turn grey; toss to coat.
Spray an 8 x 10 inch baking dish or a 8 x 12 inch rimmed baking sheet with nonstick spray and line the bottom with parchment paper.
Shingle slices of potato, laying one-third of one over one-third of another, in the bottom of the pan to form an even layer that covers the dish. With a ladle, take some of the cream from the bowl and pour just enough over the shingled potatoes to coat, about 3 tablespoons or so. Sprinkle the shingled potato generously with grated Parmesan, about ¼ cup. Broil until the cream begins to bubble and the cheese turns golden for about 1-1 ½ minutes. NOTE: Set aside your nicest largest slices for the top layer for the best presentation – but be sure to keep them covered in cream.
Sprinkle the tiny chopped broccoli florets on top of the first cooked layer of gratin. Follow by placing thin slices of prosciutto across the top. Shingle another layer of potatoes on top. Cover again with cream. Sprinkle generously again with Parmesan cheese. Brown again in the broiler until the cream bubbles and the cheese is golden brown, 1-1 ½ minutes. Remove from the oven.
Repeat step 4-5 until all of the potatoes are used up. (NOTE: Only layer prosciutto and broccoli after every other layer of potato. The final layer will be potatoes, cream and Parmesan, for a total of 5 layers.
Once the final layer comes out of the broiler, golden brown, set the oven to 375°F. Once the oven comes down to temp, place the gratin in the oven and bake until a small knife meets no resistance in the center of the gratin, 30-35 minutes.
Allow the gratin to rest for 15 minutes, then place a sheet of parchment paper over the gratin and place another baking dish or baking sheet that will fit in the pan over the parchment. Top with weights (canned goods and other pans work well) to weigh it down. Let the gratin rest with the weights for another 15 minutes. Remove the weights, pan, and parchment and slice the gratin. It’s so much easier to cut once completely cool, then you can rewarm the individual portions with some fresh Parmesan.