It is recommended to salt the chicken overnight, or for at least 3-4 hours. Pat the chicken dry and remove any strings. Liberally sprinkle 1 ½ tbsp Wild Mushroom Seasoning Salt all over the surface of the chicken, even on the back. Cover and refrigerate overnight.
Remove the chicken from the fridge two hours before you intend to roast it. Remove any covering and pat the chicken dry. Allow to come up to room temperature uncovered to allow the skin to dry off.
Preheat the oven to 400°F. Cut a thick slice from the onion and set aside to stuff the chicken; cut the remaining onion into slices. Drizzle a large roasting pan with 2 tablespoons olive oil. Scatter in the sliced onion, 3 whole garlic cloves, and 5-6 sprigs of fresh thyme. Place a rack on top of the aromatics.
Transfer the chicken to the rack in the roasting pan. Stuff the cavity with the remaining piece of onion along with 2-3 thyme sprigs. Use twine to tie the legs together tightly and tuck the wing tips under the chicken. Rub another tablespoon of olive oil over the chicken and sprinkle with the remaining ½ tbsp Wild Mushroom Seasoning Salt, or more as needed.
Roast the chicken for 1 hour 15 minutes to 1 hour 45 minutes depending on the size. Baste the chicken regularly with the pan drippings as it roasts. The chicken is done when it reaches an internal temperature of 165°F. Another foolproof way to tell the chicken is done is to tip the pan and check that the juices running from the cavity are no longer pink. Remove the chicken to a platter and let rest before carving.
Remove the rack and any large pieces of vegetables or herbs from the roasting pan. Leave 3 tbsp of the drippings in the pan. Place the roasting pan over medium high heat.
Add the flour to the roasting pan and whisk into the fat to make a roux. Let the roux cook for a minute and then deglaze with the white wine. Add the chicken broth, half a cup at a time, whisking constantly to prevent lumps. Bring the gravy to a boil and cook until thickened. Add more broth if desired to thin out the gravy. Season with Wild Mushroom Seasoning Salt to taste. Strain the gravy through a fine mesh strainer and keep warm.
Mince the remaining 2 garlic cloves. Place a large skillet over medium high heat and add 1 tbsp olive oil. When the oil is hot, add the sliced mushrooms. Sprinkle with a little Wild Mushroom Seasoning Salt and sauté for 4 to 6 minutes, tossing regularly, until the mushrooms are browned. Add the minced garlic and sauté briefly. Remove from the heat and add to the pan gravy.
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. Arrange the chicken on a serving platter and serve with the mushroom gravy. Enjoy!