|20 g||Dutch-process cocoa powder|
|20 g||black cocoa powder|
|50 g||creamy peanut butter|
|115 g||unsalted butter (cold)|
|1¾ tsp||vanilla extract|
|½ tsp||baking powder|
|355 ml||heavy cream (cold)|
|chocolate shavings (for garnish)|
Mix butter and some sugar together until combined in a food processor. Add egg and some vanilla and mix. Add baking powder, salt, cocoa powders, and flour and mix just until combined.
Heat the oven to 175°C/350°F. Divide the dough into 6 equal pieces then roll the first between 2 pieces of parchment paper until very thin and just over 17 cm/7 in. in diameter. Place flat in the freezer for approx. 10 min. Once firm, peel back the top piece of parchment paper (it should now come off cleanly when pulled gently) and use something with a 17cm/7 in. rim to trim it into a neat circle. Slide onto a baking sheet and bake for approx. 8 – 10 min. and let it cool completely on paper, which you can slide onto a cooling rack so that you can use the tray again. Repeat with the remaining dough. It sounds like a lot of work, but the best thing is to get into a pattern where one piece is being rolled while another is freezing while the third one bakes and a fourth is cooling, so you’re never working with more than one piece at a time. By the time one piece bakes, the next is ready to leave the freezer.
In a large bowl, beat the peanut butter, remaining vanilla, salt, and remaining sugar until smooth. Beating the whole time, slowly add the heavy cream, one small splash at a time, until the peanut butter cream mixture is loose enough that you can add the rest of the cream without breaking it into clumps. Whip the cream, watching it carefully (it’s very easy to overbeat with an electric mixer) until soft peaks form.
Place a bit of the whipped cream on a cake stand, then add the first cookie. Thickly frost the first cookie all the way to the edges with about 110 grams/1/2 cup peanut butter cream. Repeat with the remaining cookies, decoratively swirling the top cookie with the remaining peanut butter cream. Garnish with chocolate shavings, sprinkles, or chocolate peanut butter candy. Place the cake in the fridge overnight or, ideally, for closer to 24 hours so that the cookies soften into cake layers.