Strip the bay leaves from the spine of the leaf and tear into small pieces. Strip the leaves from the fresh thyme sprigs. Add the bay leaves to a blender or spice grinder along with the fresh thyme leaves and 1 tablespoon of kosher salt. Grind the herbs and salt until the bay leaves are broken down into small pieces.
Transfer the bay leaf salt to a small bowl. Add the remaining kosher salt and stir together. The salt can be made ahead of time.
Pat the chicken dry and remove any strings. Liberally sprinkle the bay leaf salt all over the surface of the chicken, even on the back. Reserve a little of the bay leaf salt to use later.
Place the chicken on a plate, or a small tray with a rack if possible. Refrigerate uncovered for at least 4 hours or up to overnight.
Preheat the oven to 425°F. Drizzle a little olive oil in a roasting pan and spread the sliced onion out to create a bed for the chicken to sit on. Place the chicken on top of the sliced onions. Drizzle with the olive oil and lightly rub it over the skin, trying not to remove the herbs.
Add the wine, or broth, to the roasting pan. Roast the chicken for 30 minutes.
To prepare the peaches, wash them well but leave the skins intact. Cut into quarters and remove the pits. Arrange the peaches around the chicken in the roast pan. Sprinkle with a little of the remaining bay leaf salt.
Roast the chicken for another 30 to 45 minutes until fully cooked. Check the roasting pan occasionally to make sure it doesn’t run dry. Add a splash more wine, broth, or even water if the pan becomes dry.
The chicken is done when it reaches an internal temperature of 165°F and the juices inside the cavity run clear. Remove the chicken to a platter and let rest before carving.
To serve, carve the chicken into pieces. Cut the legs off each side of the chicken and then split the drumstick from the thigh. Cut the wings off. Slice each breast off the breastbone. Slice each breast into 3 or 4 slices. Transfer the chicken to a serving platter. Arrange the peaches around the edge of the chicken and drizzle with the pan juices. Enjoy!