Remove the package of giblets from the chicken. Pull or cut out any excess fat and wash the cavity with cold running water over the sink. Thoroughly dry the bird inside and out with paper towels. Then, carefully slip your fingers between the breast skin and meat and place 2 pieces of the butter under the breast skin on each side.

Preheat the oven to 400°F.

In a round or rectangular roaster, place the onions in the middle in one layer, flat side up. Arrange the other vegetables around the onions. Then place the bird on top of the onions. Rub the olive oil all over the chicken and sprinkle salt and pepper all over the skin as well as inside the cavity. Sprinkle the herbes de Provence over the skin and inside the bird. Place the bay leaf in the bird’s cavity. Tie the legs together with kitchen twine.

Roast the chicken until the skin begins to brown, 10 to 15 minutes. Reduce the temperature to 300°F and continue roasting for about 1 hour. To test for doneness, move the leg, which should jiggle easily; pierce the thickest part of the thigh with a skewer to see if the juices run clear; or insert an instant-read thermometer into the thickest part of the thigh not touching bone, which should read 175°F to 180°F.

Remove the chicken from the roaster, transfer it to a carving board, and cover loosely with heavy-duty aluminum foil. Meanwhile, remove the vegetables from the roaster with a slotted spoon and arrange them on a platter.

To make the sauce, put the pan on the stove over medium heat. Pour in the wine and stir and scrape with a wooden spoon to deglaze the pan deposits. Continue boiling the wine for about 5 minutes to reduce and thicken it. Then, add one of the remaining butter a pieces and whisk briskly to form a thick, creamy sauce; do the same with the last butter pieces.

Carve the chicken, arranging it on the platter with the vegetables. Spoon the pan sauce over the meat. Serve immediately.