Pull the butter out about 30 minutes before starting to cook to soften it.
Combine all the seasoning (not the oil) in a small mixing bowl and mix well. Take out 2 teaspoons of the seasoning mix and add it to butter. Thoroughly combine softened butter and seasoning. Mix the rest of the seasoning with oil for the wet rub. Set both aside.
To spatchcock the chicken:
Remove the whole chicken from the packaging and remove any giblets. (Save giblets and then the back bone for homemade chicken stock.) Cut off excess fat that is often found at the bottom of the chicken, neat the tail.
Place chicken breast down on a large cutting board. All you need is kitchen shears to remove the backbone. Using the kitchen shears, cut along the spine on one side from top to bottom and then on the other side of the backbone.
Flip the chicken beast side up. Using the bottom part of the palm of your hand, put a lot of pressure in the center, right between the two breasts. Push down to flatten the breast plate until the breast plate cracks under the pressure and chicken evens out.
Cooking the chicken:
Preheat the oven to 425°.
Carefully, separate the skin from the beast meat. Flatten pieces of seasoned butter and slide it on the breast under the skin. Try to even it out as much as you can.
Rub outside of the entire chicken with the wet rub. Try to spread about 2/3 of the wet rub on the skin side and about 1/3 of the wet rub.
Cover a rimmed backing sheet with aluminum foil for easy clean up and lightly grease the foil. Place chicken beast side up onto the aluminum foil.
In a large mixing bowl, mix potatoes with oil and seasoning and spread it all around the chicken.
Place the baking sheet into the oven and bake for 40-50 minutes, depending on the size of the chicken. (You can test internal temperature of the chicken part of the breast using a meat thermometer to make sure the chicken is cooked to 165°.)
Let chicken rest for about 10 minutes before serving.