This is the description of how Jacques Pépin recommends to butterfly a chicken (it's technique #145 in Complete Techniques). I find it works better for me than Alton Brown's method, but I skip the steps to secure the leg.
- One broiler/fryer chicken - roughly three pounds
- Wash chicken, remove giblets and pat dry.
- Place the chicken on its side on a cutting board, and cut through the backbone on one side of the neck with a sturdy knife.
- Pull the chicken open and separate the backbone by cutting on the other side of the neck bone, down to the tail.
- Place the chicken skin-side down, and flatten it with a meat-pounder.
- Remove the shoulder bones that stick up by cutting at the joint.
- Remove the rib cage from each side of the chicken.
- Make a small cut at the joint which separates the thigh from the drumstick. Don't cut through, but you can cut down to the bone.
- Cut a hole through the skin between the point of the breast and the thigh.
- Push the tip of the drumstick through the hole to secure the leg.
- Cook on a grill or in a broiler about fifteen minutes per side (at 450°F).