Chocolate Swiss Roll

For the cake:
Preheat oven to 180ºC (350ºF or Gas 4). Grease a 10×15-inch cake roll pan, and line the base with parchment paper.

Using a handheld or stand mixer, beat egg yolks on high speed until thick. Gradually beat in sugar, vanilla, and yogurt. Add flour, baking powder, and cocoa powder, and mix well.

In a separate bowl, beat the egg whites and salt until stiff peaks form. Gently fold into the batter.

Pour batter into prepared pan and spread out evenly. Bake for 10–15 minutes or until a toothpick inserted in the centre comes out clean. Allow to cool in the pan for 5 minutes.

Invert the cake onto a tea towel dusted with icing (powdered) sugar. Gently peel off parchment paper, then roll up the cake with the tea towel, starting at a short end. Allow to cool completely on a wire rack.

For the filling:
Using a handheld or stand mixer, whip heavy cream until it starts to thicken. Add icing sugar and vanilla and whip to stiff peaks. Unroll the cake and spread the whipped cream evenly over the cake. Re-roll without the tea towel. Cover and chill for at least 1 hour. Dust with icing (powdered) sugar and serve.