Get the chicken out of the fridge and let it sit out on the counter to get the chill off while you get some things ready.
Line a baking sheet with foil if you like. You can skip this step, too. Lay a rack in the pan and set the contraption aside. The rack holds the chicken off the pan so that air can circulate under it as it cooks.
Combine the dry rub ingredients together in a small dish. You will only need half the mixture for this recipe so you can set aside half now to avoid contamination. Or you could just halve the recipe to begin with, but it’s lovely on seafood too, so you might as well make the extra.
Set your oven to 400º F.
Place the chicken breast-side down on a cutting board. Use heavy-duty kitchen scissors to cut out the backbone by cutting down from neck to tail along each side. Remove and discard or save for homemade chicken stock.
Open the bird up like a book. Use a sharp paring knife to cut down the center of the bird, just deep enough to incise the cartilage covering the breastbone.
Press down on the chicken now to flatten it completely. You might hear a little “pop” – that is the wish bone.
Pour the sherry all over the inside of the bird and sprinkle about 2 teaspoons of the spice mix over.
Flip the bird and brush the skin with olive oil then sprinkle another 2 teaspoons or so of the spices over the skin.
Lift the chicken onto the baking sheet/rack combo.
Bake for 45-50 minutes or until the breast meat measures 150ºF and the thigh reaches 170ºF.
Let rest 10 minutes before carving into quarters.
This dry rub is quite spicy. If you want it less so, reduce or omit the cayenne pepper.