Step 1

Remove giblets from chicken; discard or reserve for another use. Season chicken all over with 4 teaspoons salt and 11/2 teaspoons pepper, making sure to season the cavity. Stuff cavity with shallot and thyme sprigs. Let stand at room temperature 30 minutes. Meanwhile, fill lid of a 4.1-quart Römertopf clay baker with water; let stand 30 minutes to allow water to soak into lid.

Step 2

Toss together sweet potatoes, Yukon Gold potatoes, carrots, parsnip, garlic, chopped thyme leaves, remaining 1 teaspoon salt, and remaining 1/2 teaspoon pepper in bottom half of clay baker. Place chicken on top of potato mixture, and tuck wing tips under chicken.

Step 3

Drain soaking water from lid. Cover chicken with lid, and place in lower third of a cold oven. Set oven temperature to 425°F, and bake until a thermometer inserted into thickest portion of breast registers 125°F, 45 to 55 minutes. Remove lid, and continue baking at 425°F until a thermometer inserted into thickest portion of breast registers 155°F, 20 to 30 more minutes. Let rest 15 minutes before carving. (Temperature will continue to rise to 165°F as chicken rests.) Serve chicken with vegetables.