- 4 ounces pancetta small dice
- 1 cup plus 1 tablespoon whole milk
- 6 tablespoons unsalted butter
- 1/2 teaspoon kosher salt
- 1 cup all-purpose flour
- 5 large eggs 1 yolk, at room temperature
- 3 ounces grated Parmigiano Reggiano cheese
- 3 ounces grated Fontina
- 1 tablespoon fresh thyme leaves finely chopped
Heat oven to 400°F and arrange racks in the upper and lower third. Line 2 rimmed baking sheets with parchment paper or silicone baking mats and set aside. Line a plate with paper towels and set aside. Place pancetta in a medium nonstick frying pan and cook until crisp. Remove pancetta to paper towel-lined plate and set aside to drain.
Meanwhile, combine 1 cup of the milk or water with the butter and salt in a medium saucepan and bring to a simmer over medium-high heat. Reduce heat to medium-low, dump in all the flour, and stir vigorously until flour is incorporated. Cook, stirring constantly, until dough comes together in a ball and feels dry to the touch, about 2 minutes.
Transfer dough to a food processor fitted with a blade or a stand mixer fitted with a paddle attachment. Pulse or beat in five of the eggs, one by one, letting each egg completely incorporate before adding the next. Reserve 3 tablespoons of the Parmesan cheese then add pancetta, remaining cheese, and thyme; pulse or mix on low until thoroughly incorporated.
Drop tablespoon-size portions of dough on the prepared baking sheets, spacing them at least 1/2 inch apart. Whisk remaining egg yolk with the remaining 1 tablespoon milk and brush tops of cheese puffs then evenly sprinkle reserved Parmesan cheese over top. Place in oven and bake, rotating halfway through, until puffed and golden brown, about 20 to 25 minutes. Serve hot, warm, or at room temperature.