Preheat the oven to 350 F.: Warmth fills the kitchen as the oven comes up to temperature, and that gentle heat is ideal for coaxing sauce flavors to meld without drying the chicken . You should smell a faint, warm oven note when it reaches temperature. If the oven is colder than expected, cooking time will extend and the chicken could remain underdone, so always confirm the exact temperature before placing the tray inside.
Place a long piece of parchment paper in front of you and fold it in half like a book.: The parchment feels slightly stiff as you fold it, and the crease marks your forming line for the packet. Folding like a book ensures symmetric edges to seal the juices. Avoid using too small a sheet, which can make sealing awkward and encourage leaks; instead, choose a generous size so you can fold multiple times for a secure closure.
Unfold and pour about 1/4 to 1/2 cup of BBQ sauce onto the parchment paper. Place the chicken breasts on top and coat them in the sauce.: When the sauce hits the parchment it spreads in a glossy pool, and as you nestle each chicken breast into it the meat becomes shiny and sticky with sauce. Rub the sauce across the surface to ensure every bite will be seasoned. A common oversight is skimping on sauce, which yields drier, less flavorful results, so err on the side of enough sauce to fully coat the meat.
Fold the parchment paper over, and starting at one end of the parchment, fold the edges of the paper over several times continuing to make creases all around the chicken until it’s completely enclosed and no air can escape.: As you fold, the packet compresses, and you can hear the faint crinkle of the paper forming tight seams. Proper sealing traps steam, which is the key to tenderizing the chicken . If the packet is not sealed firmly, steam will escape and the meat can dry out, so take your time creating multiple creases until the enclosure feels solid.
Place the parchment packet on a baking sheet and bake for 30 minutes.: The baking sheet will take on warm radiance as it goes into the oven, and after about 20 minutes you may detect a sweet, smoky perfume escaping when you carefully open the oven briefly. The chicken should be opaque and easily pierced with a fork when done, and the sauce inside will be hot and slightly thickened. Overbaking is the main hazard here, resulting in firm, less juicy meat, so resist the urge to extend time unless you check with a thermometer for doneness.