Combine milk, 1/4 cup butter, and a pinch of salt in a saucepan; bring to a boil. Whisk semolina into boiling milk, mixing well to prevent lumps. Reduce heat and cook, stirring often, until thickened, 3 to 4 minutes. Remove saucepan from heat. Add egg yolks, 1 cup Grana Padano, and Gruyere cheese; stir well.

Heat a nonstick skillet over medium heat; cook and stir pancetta until crisp, 7 to 10 minutes. Stir pancetta into semolina mixture.

Preheat oven to 350 degrees F (175 degrees C). Grease 2 baking sheets with 1 1/2 teaspoon butter.

Spread semolina mixture onto one of the prepared baking sheets, about 1/2-inch thick. Allow to cool to room temperature, about 15 minutes.

Cut small disks out of cooled semolina using a juice glass or cookie cutter. Place the disks onto the other prepared baking sheet, slightly overlapping the disks. Sprinkle the remaining Grana Padano cheese over disks and dot with remaining 1 1/2 teaspoon butter.