- Preheat the oven to 180°C/160°C fan/gas mark 4. Grease a 33 x 22cm swiss roll tray, or shallow baking tray.
- Line the base with greaseproof paper and set it aside.
- For the decorative sponge paste, cream the butter and icing sugar together until light and fluffy, gradually adding the egg white and beating continuously.
- Fold in the flour and spoon the mixture into a piping bag fitted with a plain piping nozzle.
- Pipe a pattern across the greaseproof paper already placed on the baking tray; swirls, flowers, stars, snowflakes, hearts, it’s up to you!
- Keep the tray in the fridge while you make the cake batter.
- To make the roulade sponge, mix together the flour, cocoa powder, baking powder, bicarbonate of soda and salt in a medium bowl.
- Whisk the eggs until thick, pale and fluffy. Add the oil and sugar, and beat until combined.
- Then add the buttermilk, white wine vinegar, vanilla extract and red food colouring (start off with 1/4 teaspoon and add more if needed).
- Gradually add the dry ingredients until you have a consistent texture.
- Carefully pour the batter into the prepared pan and bake for 13 to 15 minutes, or until a thin skewer inserted into the centre comes out clean.
- Dust a bit of icing sugar onto a clean tea towel. Once ready, immediately loosen the edges of the baking paper away from the edge of the tin and invert the sponge onto a cooling rack.
- Once cool enough to touch, peel away the paper, then gently flip the cake (decorative pattern facing downwards) onto the sugar-dusted tea towel.
- Roll the sponge and the towel up together with the decorative side facing outward. Allow to cool completely on a wire rack, seam-side down.
- For the filling, mix together the cream cheese and butter, then add the icing sugar, and beat until smooth and fluffy.
- Gently unroll the cooled cake, and spread the filling over the (plain) inside of the sponge. Re-roll the sponge (without the tea towel) and chill seam-down for at least 1 hour before serving.