5 ounces pancetta, cut into 1/2-inch pieces
2 tablespoons finely chopped shallot
1/4 teaspoon salt
1 teaspoon fresh thyme leaves
1 cup heavy cream
PAM Original Cooking Spray
1 1/2 pounds Russet potatoes, peeled and thinly sliced
1/2 cup finely grated Gruyere
1/4 cup finely grated Parmigiano Reggiano
Preheat the oven to 375°F and line a plate with a paper towel. Add the pancetta to a medium skillet over medium heat and cook, stirring occasionally, until crispy, 7-10 minutes. Use a slotted spoon to move the pancetta to the paper towel-lined plate. Drain off most of the rendered fat, leaving a thin coating. Add the shallot, salt, and thyme and saute until the shallot is translucent, 2-3 minutes. Stir in the heavy cream and cook, stirring often, until hot. Remove from the heat.
Spray a 1-quart gratin or baking dish with PAM Original Cooking Spray. Line the bottom of the dish with about 1/3 of the potato slices, sprinkle with 1/2 the pancetta and 1/4 cup Gruyere. Add another layer of 1/3 of the potato slices, the remaining 1/2 of the pancetta, and remaining 1/4 cup Gruyere. Add the final 1/3 of the potato slices in concentric circles. Pour the hot heavy cream mixture evenly over the gratin.
Cover with aluminum foil and bake until the potatoes are pierced easily with a fork, about 45 minutes. Remove the foil and sprinkle evenly with the Parmigiano Reggiano and return to the oven to bake until the cheese is melted, about 15 minutes. If you would like additional browning on the top of the gratin, place under the broiler until golden, 2-3 minutes. Rest at least 15 minutes before serving warm.