Pat the galletti completely dry and place breast-down on a cutting board. Using kitchen shears, cut along both sides of the backbone and remove it.

Flip the birds breast-up and press firmly on the breastbone until you hear it crack and each bird lies flat.

Whisk 2 tbsp olive oil, garlic, lemon zest, chili flakes, salt, and pepper in a small bowl. Rub the mixture over and under the skin of both birds, then tuck a rosemary sprig under the skin of each. Let sit at room temperature for 20 minutes.

Wrap two bricks tightly in foil, or set aside a heavy 25 cm / 10-inch skillet loaded with a couple of cans to use as the weight.

Heat the remaining 2 tbsp olive oil in a 30 cm / 12-inch cast iron skillet over medium-high heat until shimmering.

Working with one galletto at a time, lay it skin-side down in the skillet and set the foil-wrapped bricks directly on top to press it flat. Cook undisturbed for 18 to 20 minutes, until the skin is deep gold and crackling.

Remove the bricks, flip the bird, and cook 8 to 10 minutes more, until an instant-read thermometer at the thickest part of the thigh reads 165 F / 74 C.

Transfer the first galletto to a sheet pan and keep warm in a low oven at 95 C / 200 F while you repeat the searing process with the second bird, adding more oil to the pan if it looks dry.

Once both birds are cooked, let them rest under loosely tented foil for 10 minutes.

Add the butter and a squeeze of lemon to the hot skillet, scraping up any browned bits, and spoon the pan juices over the carved galletti. Serve with the remaining lemon wedges.