1. 1. Preheat your oven to 475°F (245°C). Line a baking sheet with parchment paper.

2. 2. In a medium bowl, whisk together the flour, potato starch, cocoa powder, and baking powder.

3. 3. In a large mixing bowl, beat the eggs and 1 cup of sugar until light and fluffy, about 3-4 minutes.

4. 4. Gradually mix in the dry ingredients until fully incorporated and the batter is smooth.

5. 5. Spread the batter evenly onto the prepared baking sheet.

6. 6. Bake for 5-7 minutes or until the edges turn lightly golden and the cake springs back when lightly touched.

7. 7. While the cake is still warm, carefully roll it up in the parchment paper and let it cool completely on a wire rack.

8. 8. Once cooled, unroll the cake and spread the lemon curd evenly over the surface, leaving a 1/2 inch border.

9. 9. In a clean mixing bowl, beat the heavy cream, vanilla extract, and 2 tbsp of sugar until stiff peaks form.

10. 10. Spread most of the whipped cream over the lemon curd, reserving some for garnish.

11. 11. Carefully roll the cake back up tightly, using the parchment paper to help guide the rolling.

12. 12. Wrap the rolled cake in plastic wrap and refrigerate for at least 1 hour or until firm.

13. 13. When ready to serve, unwrap the cake and slice it into 1-inch thick pieces using a sharp, serrated knife.

14. 14. Garnish each piece with a dollop of reserved whipped cream and a sprinkle of lemon zest, if desired.