Marshmallow Swiss Roll Cake

Method 

1. Preheat oven to 190˚C. Line a 22 x 33 cm baking sheet with baking paper and set aside.
2. In a bowl, beat together the egg yolks and sugar for about 60 seconds.
3. Add the oil, milk, and vanilla essence and combine.
4. Sift in the flour and cornstarch and beat until smooth. Set aside.
5. In a separate bowl, whip the egg whites until frothy. Add the vinegar and sugar and whip until you achieve soft peaks.
6. Gently fold the whipped whites into the egg yolk mixture in 2-3 sections until fully combined.
7. Pour the prepared batter into the prepared baking sheet and smooth out the top.
8. Bake for 14-15 minutes or until golden. While the cake is baking, lay a clean kitchen towel on a work surface and evenly sprinkle it with 30g granulated sugar.
9. As soon as the cake is baked, lift it out of the baking sheet and immediately flip it over onto the prepared kitchen towel. Peel off the paper and roll up the cake with the kitchen towel.
10. Allow to cool down to room temperature before moving onto the next step.
11. For the filling, place the marshmallows and water in a large microwave-safe bowl. Microwave on high, stirring occasionally, until melted.
12. Using a spatula, spread the marshmallow mixture on top of the gently unrolled cake. Then roll the cake back up.
13. Cover the cake roll and let it chill in the refrigerator for at least 3 hours before slicing. Dust with powdered sugar and top with fresh berries before serving.