1 1/2 cups whole milk
8 tablespoons unsalted butter (1 stick)
1 tablespoon kosher salt
1 teaspoon freshly ground black pepper
1 1/2 cups all-purpose flour
5 large eggs
1 cup shredded aged (3 to 6 months) Manchego cheese (about 3 ounces) or Idiazabal
1/2 cup finely grated Parmesan cheese (about 1 ounce)
1. Heat the oven to 375°F and arrange racks in the upper and lower third. Line 2 baking sheets with silicone baking mats or parchment paper.
2. Combine milk, butter, salt, and pepper in a medium saucepan and bring to a boil over medium heat. Reduce heat to low, add flour all at once, and stir vigorously until well incorporated. Cook, stirring constantly, until dough feels dry to the touch and is no longer sticking to the bottom of the pan, about 3 to 5 minutes. (The dough will form one large ball.)
3. Transfer dough to a mixer fitted with a paddle attachment. Beat in eggs one at a time on medium-low speed, letting the first one completely incorporate before adding the next. Reserve 3 tablespoons of the shredded Manchego cheese. Add remaining Manchego and Parmesan cheese to dough and mix on low until incorporated.
4. Drop tablespoon-size rounds of dough on the prepared baking sheets, about 1/2 inch apart. Evenly sprinkle reserved Manchego cheese over top. Bake, rotating halfway through baking time, until puffed and golden brown, about 30 to 35 minutes. Serve hot, warm, or at room temperature.