Preheat the oven to 425F and set a rack in a large roasting pan.

Pat both chickens dry inside and out with paper towels; a dry skin crisps, a damp one steams.

Mix the softened butter with the minced garlic, rosemary and thyme in a small bowl.

Loosen the skin over each breast with your fingers and push half the herb butter under the skin of each bird, then rub any remaining butter over the outside.

Season both chickens generously, inside and out, with salt and pepper.

Stuff each cavity with a halved lemon and a halved head of garlic.

Tie the legs together with kitchen twine and tuck the wing tips under the body.

Drizzle the skin with olive oil and place both birds breast-side up on the rack, leaving space between them for air to circulate.

Roast for 50 to 60 minutes, rotating the pan once halfway, until an instant-read thermometer in the thickest part of the thigh reads 165F and the juices run clear.

Let rest, loosely tented with foil, for 15 minutes before carving; this keeps the juices in the meat instead of on the cutting board.