1. Place the chicken on your work station with the legs down on a cutting board and the neck facing you. Using a sharp pair of kitchen shears, cut along the spine, using the neck as a guide for thickness. It should be fairly easy to cut. Cut along both sides of the spine until it is fully detached. Reserve the spine for chicken broth or stock.
2. With the skin side up, flatten the chicken on your work station, using the palm of your hand to break the breastbone (the bone between the two chicken breasts). If you don’t hear or feel it crack, flip the chicken over and cut the breastbone with the kitchen shears. Lay the chicken on a baking sheet lined with Gefen Parchment Paper, pat dry, and allow to rest in the fridge for one hour, or up to eight hours.
3. Preheat oven to 425 degrees Fahrenheit (220 degrees Celsius).
4. Remove chicken from fridge and pat dry again. Take three tablespoons of onion salt and mix with olive oil until you have the texture of wet sand. Liberally rub all over the chicken – under the wings, all around the legs, etc. – making sure all exposed skin and meat is covered.
5. Bake 45 minutes, then allow to rest for five minutes. Serve.