Preheat oven to 350°F. Line 2 cookie sheets with parchment or silpat baking mats.: As you heat the oven to 350°F , notice the warm air that will soon crisp the edges of the cookies, and line your trays with parchment or silpat so the bottoms do not brown too quickly. The smell of the oven warming signals that baking is imminent. A common mistake is not preheating fully, which can cause uneven spread and texture, so wait until the oven reaches temperature. Also, make sure the racks sit evenly so the cookies bake consistently. If your sheets are thin, rotate them midway to avoid hot spots.
Cream butter, peanut butter, and both sugars in the bowl of an electric mixer fitted with the paddle attachment. Add egg, vanilla, milk, and salt and baking soda. Mix until combined. Slowly add flour and mix until dough comes together.: When creaming unsalted butter , peanut butter , brown sugar , and granulated sugar , listen for the change to a lighter, slightly fluffy sound as air incorporates, which helps create a tender bite. Adding the egg , vanilla , milk , salt , and baking soda keeps the batter cohesive and flavorful, and slowly folding in the all purpose flour prevents overworking the gluten. You should stop mixing as soon as the dough forms; a tacky, slightly sticky dough indicates proper moisture. Overmixing will toughen the cookies, and undermixing leaves pockets of dry flour. Scrape the bowl to ensure even distribution.
Scoop 1 tablespoon sized balls of dough. Place on cookie sheet 2" apart. Press lightly with your palm to flatten to about 1/2" thickness. Use your thumb and forefinger to pinch the ends to make the cookies look like footballs.: As you portion dough into 1 tablespoon balls, feel the pliable texture that holds shape yet yields to gentle pressure. Placing them about 2" apart prevents merging while allowing edges to crisp. Flatten to roughly 1/2" so the centers remain soft after baking, and use your thumb and forefinger to create tapered ends, forming the football silhouette. A common slip is making them too flat, which results in over crispness, or too tall, which prevents the chocolate filling from sitting properly. Keep each cookie uniform so baking time stays consistent.
Bake for 8-10 minutes, until they just begin to brown. Cool completely on cookie sheets.: While baking for about 8 to 10 minutes, pay attention to the visual cue of the edges turning a light golden brown while the centers remain slightly soft. The kitchen will fill with the toasty scent of peanut butter and caramelized sugar, and you may hear faint crackles as edges set. Letting the cookies cool fully on the sheets helps them finish setting without collapsing. A frequent mistake is removing them too soon and moving them, causing them to break; let them rest until firm to the touch. If your oven runs hot, check a minute or two earlier to avoid overbrowning.
Melt the chocolate chips with the crisco or oil, heating in 30 second increments, stirring after each, until smooth. Place chocolate in a ziploc bag and cut off a teeny tip (or use a squirt bottle). Outline the football shape on the cookie, then fill in with the chocolate. Tap the cookie sheet to even out any wrinkles in the chocolate, then chill to harden.: Melting the chocolate chips with a teaspoon of Crisco or vegetable oil yields a glossy, fluid ganache that flows into the football cavity. Heat gently in 30 second bursts and stir until silky; overheating causes graininess and a dull finish. Pipe an outline and then fill the center, watching how the chocolate levels when you tap the sheet gently, creating a smooth surface. Chill briefly so the chocolate firms cleanly. A common error is piping chocolate while it is too hot, which can soak into the cookie and make it soggy; allow it to cool slightly before filling.
Make the laces with a little white frosting or some melted white chocolate chips. (White frosting is easier!): The final touch is the delicate white laces , which contrast beautifully with the dark filling and complete the football look. Use a small piping tip or a tiny cut on a ziploc bag to draw a center line and stitch marks. The texture of the white icing should be thick enough to hold shape but soft enough to pipe smoothly, and if you use melted white chocolate chips , let them cool a little so they do not run. A frequent mistake is applying the laces while the chocolate filling is still warm, causing smudging; wait until the filling is set.
Store in an airtight container for up to 3 days.: When cooled and decorated, stacking the cookies with parchment layers in an airtight container preserves their texture for up to 3 days. The container will keep the crisp edges from going stale while maintaining the soft centers. If you live in a humid area, add parchment between layers to prevent sticking. The usual misstep is leaving them uncovered, which dries them out quickly, so seal tightly and store at room temperature.