To make the icing: bring a few inches of water to a boil in a saucepan that can hold a standing mixer's bowl above the water. Whisk the sugar, the egg whites, lemon juice, or cream of tartar, and salt in the bowl by hand. Set the bowl above the boiling water and continue whisking until the mixture is hot to the touch and the sugar dissolves, about 1 to 2 minutes. Transfer the bowl to a standing mixer fitted with the whisk attachment and beat the whites at medium-high speed until they almost hold a stiff peak and are fully cooled, about 10 minutes. Beat in the butter, a little at a time, until the icing is smooth and spreadable. (If the icing separates, just keep beating and it will come back together.)
To decorate the cake: Divide the icing in half. Set aside a couple of tablespoons white icing for field line. Blend a few drops of green food coloring into 1 portion so it is the same color as football field turf. Beat the cocoa powder and melted chocolate into remaining icing.
Cover sides of the cake with chocolate icing. (Save some chocolate icing to decorate football cookie, if desired.)
Transfer the green icing to a pastry bag fitted with a small tip, and cover the top of the cake, moving back and forth in small motions to create the turf. Clean bag and tip thoroughly, fill with white icing and add yard lines to field as desired.
Pressed football themed cookies into the top or sides of the cake, as desired, and finish with plastic goal posts.
Serve or set aside at room temperature for up to 2 hours before serving, refrigerate if needed. (If cake is refrigerated, bring to room temperature 1 hour before serving.)
To make the cookies: whisk the flour and salt in a medium bowl.
Beat the butter and sugar in another medium bowl with an electric mixer on medium-high speed until light and fluffy, about 3 minutes. Add the egg and vanilla mixing until fully incorporated. Slowly add the flour mixture, and continue beating just until the dough comes together, stopping and scraping down the sides of the bowl as needed.
Divide dough in half, pat into disks, wrap in plastic wrap and refrigerate until firm, at least 4 hours and up to overnight.
Generously flour a clean work surface. (Tip: for a nice, even layer of flour, sift flour over work station.) Roll chilled dough about 1/4-inch thick. Cut into desired shape using a cookie cutter, working quickly enough that the dough stays chilled. (If dough gets warm and soft, put it in refrigerator on a lined baking sheet to chill, about 30 minutes.) Transfer cut cookies to un-greased baking sheets, leaving about 1-inch between cookies. Lightly dust off excess flour with a dry pastry brush. Refrigerate the formed cookies for at least 30 minutes. (Excess dough can be gathered together, pressed into a disk, chilled and rerolled.)
Preheat the oven to 160°C. Bake the cookies, until the bottoms and sides are barely golden, about 12 to 15 minutes depending on shape. Cool on the baking sheets until firm enough to transfer to a rack to cool. Decorate as desired and serve. Store in an airtight container at room temperature for up to 1 week.
Yield: 1 1/2 dozen cookies, depending on shape
For the cake: Position a rack in the lower third of the oven and preheat to 175°C. Butter and line the bottom of 9 by 13-inch cake pan with parchment paper, overlapping on 2 sides to create flaps.
Put chopped the chocolate in a bowl. Heat cola just to a simmer over low heat and pour over chocolate. Let stand for 5 minutes; stir until smooth.
Whisk together the flour, cocoa powder, baking soda and salt in a medium bowl.
In another large bowl, beat the eggs and sugar with an electric mixer on medium speed until slightly thickened and pale, about 3 minutes. Gradually add the oil, buttermilk, vanilla, and melted chocolate mixture to eggs. Beat on low until combined well, but not aerated. Add the flour mixture and continue to beat until just combined. (Stir lightly with a rubber spatula to remove any pockets of flour.) Pour the batter into the prepared pan and bake until the cake springs back lightly when touched, and a tester inserted in center comes out clean, about 40 minutes.
Cool cake completely in the pan on a rack. Run a knife around edge of the pan and invert cake onto a rack. Carefully remove parchment paper and cool completely. (The cake may be made in advance, tightly wrapped and kept at room temperature for up to 2 days.