America's Test Kitchen is one of my favorite sites. And, when they invited me to a reduced price year's subscription, I snatched it up. This recipe was in the magazine that they sent me. Unfortunately, we can't "pinch" directly from their site. . . This is the unadorned version, though they have 4 variations available. And, once you can get the meat in the right formation (butcher's tend to shred the skin, and they really just want to split that breast, both of which RUIN this recipe), it's easy and delicious!
First, the chicken: this recipe relies entirely on the breast bone still attaching both breasts together and the skin needs to be still attached. Either cut a whole chicken yourself (and don't destroy the skin!), or have a butcher do it, but WATCH THEM -- don't accept a split breast or tattered skin! Also, it's confusing, but you need TWO -- that is, two chest pieces (two separate birds).
Adjust oven rack to middle position; heat oven to 450*F. Line bottom of broiler pan with foil; place broiler pan rack on the top and set aside.
In a small bowl, mix 1/2 tsp salt and butter until combined.
Sprinkle underside of chicken with salt and pepper. Carefully lift the skin from the meat, coming in from one edge. Try to keep the edges attached, as much as possible -- a 2" hole should allow you plenty of room to work. Carefully maneuver half of the butter mix under the skin and smooth over the meat. Repeat for the other chickie. Smooth the vegetable oil over top of the skin of both and sprinkle liberally with pepper.
Set both on broiler pan. Roast until thickest part of breast registers 160*F, 35 - 40 minutes. Transfer chicken to cutting board and let rest for 5 minutes. Split the breast by coming down the middle and sliding knife along the breast bone and over the ribs (much easier said than done). Serve immediately.