Preheat your oven to 350°F (175°C). Lightly grease a 10x15-inch jelly roll pan, line it with parchment paper, and lightly grease the parchment. Dust a clean, lint-free kitchen towel generously with cocoa powder.

In a large bowl, whisk the 4 egg yolks, 1/4 cup (50g) of the granulated sugar, vegetable oil, buttermilk, and vanilla until pale and frothy. Sift the cake flour, Dutch-processed cocoa powder, baking powder, and salt directly into the yolk mixture. Fold gently until just combined.

In a separate clean bowl, whip the 4 egg whites until soft peaks form. Gradually pour in the remaining 1/4 cup (50g) of granulated sugar while mixing on high speed. Whip until stiff, glossy peaks form. Gently fold the meringue into the chocolate batter in three batches.

Spread the batter evenly into your prepared jelly roll pan. Use an offset spatula to smooth the surface. Bake for 10 to 12 minutes until the top springs back slightly when pressed.

Immediately turn the hot cake out onto your cocoa-dusted kitchen towel. Peel off the parchment paper. While still steaming hot, roll the cake up tightly from the short end, with the towel inside. Cool completely on a wire rack for 1 hour.

Beat the softened cream cheese and creamy peanut butter until smooth. Add the sifted powdered sugar and vanilla extract. In a separate chilled bowl, whip the heavy cream until stiff peaks form. Fold the whipped cream into the peanut butter mixture.

Unroll the cooled sponge. Spread the peanut butter filling evenly over the surface, leaving a 1/2-inch border. Gently re-roll the cake without the towel. Wrap in plastic wrap and chill in the refrigerator for at least 2 hours.

Microwave 1/3 cup of heavy cream until simmering, pour over the dark chocolate chips, let sit for 2 minutes, then whisk until smooth. Drizzle over the chilled cake roll. Sprinkle immediately with powdered sugar, chopped peanut butter cups, and crushed peanuts.