Step 1

Adjust oven rack to middle position and heat oven to 475 degrees. Toss shallots, potatoes, carrots, parsnips, 1 tablespoon oil, ½ teaspoon salt, and ½ teaspoon pepper together in bowl. Spread vegetables evenly into 16 by 12-inch roasting pan. Spray V-rack with vegetable oil spray and nestle into pan with vegetables.

Step 2

Pat chickens dry with paper towels, tie legs together with kitchen twine, and tuck wingtips behind back. Using fingers, gently loosen skin covering breasts and thighs. Spread 3 tablespoons tarragon under skin of chickens, directly onto meat.

Step 3

Season exterior of chickens with salt and pepper. Place chickens, breast side down, in prepared V-rack. Roast for 20 minutes.

Step 4

Flip chickens breast side up and continue to roast until breasts register 160 degrees and thighs register 175 degrees, 50 to 60 minutes.

Step 5

Remove pan from oven. Transfer chicken to carving board, tent loosely with aluminum foil, and let rest for 15 minutes. Being careful of hot pan handles, place pan over medium-high heat on stovetop (over 2 burners, if possible) and cook vegetables, stirring gently, until lightly browned and glistening, 8 to 10 minutes.

Step 6

Whisk remaining ¼ cup oil, remaining 3 tablespoons tarragon, parsley, vinegar, and mustard together in small serving bowl. Carve chickens and serve with vegetables and vinaigrette.