Instructions

1. For the Cake: Preheat the oven to 180C/350F/Gas 4. Spray or butter a 13x9" Swiss roll pan, line with parchment paper, then spray again. Set aside.
2. In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt.
3. Using a handheld or stand mixer, beat the eggs until pale, and frothy. Add the oil and sugar, and beat until combined. Add the buttermilk, vinegar, red food colouring (enough to reach desired shade), and vanilla extract, and beat until combined. Gradually add the dry ingredients until just combined.
4. Pour the batter into the prepared pan, and bake for 15 - 20 minutes, or until a toothpick inserted into the centre comes out clean.
5. Immediately loosen the edges of the cake and invert the sponge onto a tea towel dusted with icing sugar. Peel away the paper, then gently roll the sponge and the towel up together. Cool completely on a wire rack, seam side down.
6. For the Filling: Using a handheld or stand mixer fitted with the paddle attachment, beat the cream cheese, and butter until smooth. Add the icing sugar, and beat until smooth and fluffy.
7. Gently unroll the cooled cake, and spread the filling over the inside of the sponge. Re-roll the sponge without the tea towel, wrap in clingfilm, and chill for at least 1 hour before serving.