2 ounces pancetta, diced 1 leek, cut in half and thinly sliced into half-moons (light green and white part only!) ½ yellow onion, thinly sliced into half-moons ¼ head of green cabbage, shredded 2 ½ cups heavy cream 3 cloves garlic, finely minced 2 teaspoons salt 2 teaspoons finely minced fresh thyme 1 teaspoon freshly grated black pepper 3 pounds potatoes, washed and very thinly sliced 1 cup grated Grana Padano 1 tablespoon finely chopped green onion
Preheat oven to 325 degrees Fahrenheit. Heat a sauté pan over medium heat. Add pancetta and cook until lightly crisped. Add leek and onion, sautéing until just translucent, then add in cabbage and cook until wilted and reduced in size by about a quarter. Pull from heat and set aside.
Meanwhile, thoroughly coat a baking dish or round pie plate with butter. In a mixing bowl, combine cream, garlic, salt, thyme and black pepper and set aside. Cover the bottom of the baking dish with a single layer of potatoes, allowing the corners to overlap slightly so that there are no empty spaces. Add half of the cabbage mixture. Continue with another layer of potatoes, then cabbage, then potatoes.
Pour cream mixture evenly into baking dish, then press down on the top of the gratin to allow mixture to ooze into every corner and compress layers.
Cover with aluminum foil and bake for 45-60 minutes, until potatoes are fork tender. Remove foil, top with Grana Padano, and broil until cheese is bubbly and golden brown. Cool slightly, top with green onions and serve!