Preheat the oven to 375°F. Line two baking sheets with parchment paper.
In a medium saucepan, combine milk, butter, salt, and pepper and bring to a boil. Reduce heat, add the flour and stir vigorously until well incorporated.
Stirring constantly, cook the dough until it begins to feel dry to the touch and forms a ball that does not stick to the bottom of your saucepan. Remove from heat.
Using a rubber spatula, begin to beat in eggs one at a time, thoroughly blending in the last before adding the next.
Set aside 3 Tbsp. of the Manchego, and add the remaining Manchego and all of the parmesan cheese to the dough. Mix gently and consistently until thoroughly incorporated.
Using a Tbsp. or large dinner spoon, begin dropping rounds of dough onto the lined baking sheets about 1/2 inch apart. Evenly sprinkle the set-aside Manchego cheese over the top of the dollops.
Bake until puffed and golden brown, about 30 to 35 minutes.
Serve hot, cold or at room temperature. Store in a plastic container with a lid in the refrigerator.
