- 2 1/2 lemons
- 2 quarts buttermilk
- 4 garlic cloves, crushed
- 2 tablespoons kosher salt plus more
- 2 3 1/2- to 4-pound chickens
- 1 bunch fresh marjoram
- 1/4 cup (1/2 stick) unsalted butter, room temperature
- Freshly ground black pepper
- 1 small shallot, finely chopped
- 1/2 cup olive oil
- 1/3 cup Champagne or white wine vinegar
- 1 loaf country-style bread or ciabatta, crust removed, torn into 1 1/2″ pieces (about 8 cups)
- 2 bunches watercress, thick stems trimmed (about 8 cups)
- Thinly slice 1 lemon. Whisk buttermilk, garlic, and 2 tablespoons salt in a medium bowl. Divide buttermilk mixture and lemon slices between 2 large resealable plastic bags. Place 1 chicken in each bag and seal, pressing out any excess air. Refrigerate, turning occasionally, at least 8 hours and up to 1 day.
- Preheat oven to 425°F. Remove chickens from marinade, rinse with cold water, and pat dry. Thinly slice half of a lemon; cut remaining whole lemon in half. Place chickens on a wire rack set inside a large rimmed baking sheet; stuff each with 1/2 bunch of marjoram and a lemon half. Working from neck end of chicken, gently loosen skin from chicken breasts. Place several lemon slices under skin of each breast. Rub chickens with butter; season with salt and pepper. Tie legs with kitchen twine and tuck wing tips under chicken.
- Roast chickens until they begin to brown, 30-35 minutes. Reduce oven temperature to 350°F and roast until chickens are cooked through and a thermometer inserted into the thickest part of the thigh registers 165°F, 20-25 minutes longer. Transfer chickens to a platter, tent with foil, and let rest while preparing bread salad. Keep oven on.
- Carefully pour chicken roasting juices from baking sheet into a large bowl (set baking sheet aside). Whisk shallot, oil, and vinegar into juices in bowl; season vinaigrette with salt and pepper.
- Pour half of vinaigrette into a small bowl; set aside. Add bread to vinaigrette in large bowl and toss, pressing gently to help bread absorb vinaigrette.
- Transfer bread to reserved baking sheet and toast, tossing occasionally, until bread is golden brown but still soft in the center, 10-15 minutes (set bowl aside).
- Place warm bread in reserved bowl. Add watercress and reserved vinaigrette; season with salt and pepper and toss to combine. Arrange salad on a platter and place chickens on top.