With poultry shears, cut along both sides of the backbone of each chicken to remove it. Lay the chicken out flat, skin side down. With a small, sharp knife, make an incision along both sides of the breastbone, then use your fingers to pry the keel-shaped breastbone out. With the knife, cut away the small rib bones and the wishbone, which runs along the front and thickest part of the breastbone.

Pat the chickens dry with paper towels and season them generously with coarse salt and pepper. In a large bowl, combine the olive oil, garlic cloves, and rosemary. Turn the chickens gently in this marinade until coated. Cover with plastic wrap, then refrigerate, turning the chickens once or twice in the marinade, for at least 8 hours, or overnight.

Heat a griddle over medium-high heat until a drop of water evaporates almost immediately on contact, or place one or more heavy stovetop griddles or large cast-iron skillets over medium-high heat. Place the chickens on the griddle or skillet, skin side down, and weight them down with a clean skillet or bricks wrapped in aluminum foil. The weights should be applied so they press the greatest amount of skin down in contact with the cooking surface as possible. Cook until the skin is deep golden brown and crispy, 7 to 10 minutes. Resist the temptation to peek at the skin for at least the first 3 or 4 minutes: The longer the chicken cooks undisturbed, the less likely it will be to stick. Turn the chickens over, gently releasing the skin with a metal spatula if it sticks in places. Weight the chickens again and continue cooking until the other side is deep golden brown and crispy and the chicken is cooked through, with no trace of pink, about 7 minutes. The chicken should be crispy but still juicy. Serve immediately.

Note: Most spring chickens weigh about one pound, but it is possible to find this smaller size. The size of the chickens, and the means you have to cook them, will determine how many chickens you can serve. In other words, you should estimate how many chickens, when deboned and lying flat, will fit on your griddle or portable griddle or in your cast-iron skillet(s). If you don’t have the room for 6 chickens, decrease the proportions of the other ingredients accordingly. Also, this recipe is delicious when prepared on a charcoal grill. Make sure the grill is clean and free of residue and resist the temptation to peek at the skin for the first several minutes. Most foods will stick to the grill at first, but will release themselves after a few minutes.