2 cups packed parsley leaves
1/4 cup fresh thyme leaves
1/4 cup fresh rosemary leaves
4 cloves garlic, peeled
1 1/2 tbsp extra-virgin olive oil
2 tsp salt
Freshly ground pepper, to taste
2 whole chickens
1 cup reduced-salt chicken broth, divided
1/2 cup dry white wine
2 tbsp water mixed with 1 tablespoon cornstarch
Position oven rack in lower third of oven; preheat to 175 degrees celsius. Coat a large roasting pan with cooking spray.
To prepare chickens:
Zest lemons, then cut in half. Combine lemon zest, parsley, thyme, rosemary, garlic, oil, salt and pepper in a food processor or blender; process until finely chopped.
Reserve 1/4 cup of the mixture, covered, in the refrigerator for the gravy.
Remove excess fat from chickens. Dry insides with a paper towel. With your fingers, loosen skin over breasts and thighs to make pockets, being careful not to tear the skin.
Spread 1/4 cup herb mixture in the pan; place the chickens on top, at least 1 inch apart.
Rub 1 tbsp herb mixture into each cavity; spread remaining mixture under skin. Place 2 lemon halves in each cavity. Tuck wings behind the back and tie legs together.
Roast the chickens for 20 minutes. Drizzle with 1/4 cup broth and roast for 40 minutes more, basting with pan drippings every 20 minutes.
Tent the chickens with aluminum foil and continue roasting for 30 minutes, or until an instant-read thermometer inserted into the thickest part of the thigh, away from the bone, registers 82 degrees and the cavity juices run clear.
To prepare gravy:
Transfer the chickens to a platter; tent with foil. Pour pan juices into a bowl. Chill juices in the freezer for 10 minutes. Meanwhile, add wine and remaining broth to the pan; bring to a boil over medium heat, scraping up any browned bits. Add any juices accumulated on the platter.
Skim fat from the chilled juices. Add juices to the pan; return to a boil, then strain into a saucepan. Bring to a simmer. Whisk in cornstarch mixture.
Simmer, stirring, until slightly thickened, about 1 minute. Stir in reserved herb mixture. Season with pepper.