Pat the chicken dry with a paper towel. Evenly sprinkle the 2 tbsp of salt and pepper over the chicken and inside the cavity. Refrigerate uncovered overnight.

Preheat the oven to 400F. Mix together the softened butter and sage. Spread the mixture over the chicken and underneath the skin. Place the crushed garlic and quartered onion in the cavity of the chicken.

Toss the diced vegetables with the olive oil and season with salt and pepper. Lay the vegetables on a roasting pan and place the chicken on top. Tuck the wings underneath the chicken and tie the legs together to ensure an even cooking.

Roast the chicken for approximately 45 minutes to an hour until golden brown and cooked through. The juices should run clear and the internal temperature reads 160F.

Remove the vegetables and chicken and let it rest on the side. Place the roasting pan on medium heat. Add 2 tbsp of flour and whisk to combine with the drippings. Cook and stir for one minute.

While whisking, stream in the 2 cups of stock. Cook and whisk until it bubbles and thickens. Season with salt and pepper.