The cake

1. Preheat your oven to 475°F 

2. Butter up a parchment paper and place on a cookie sheet.

3. In a stand mixer, with the whisk attached, beat the eggs and sugar until light and fluffy, about 5 minutes.

4. In a separate bowl, sift together the potato flour, baking powder and cacao powder.

5. Carefully fold the dry mixture into the egg mixture until no dry bits remain.

6. Spread the batter evenly on top of the parchment paper.

7. Bake in the middle of the  pre-heated oven for about 5 minutes.

8. While the cake bakes, lay out another piece of parchment paper on a work surface and sprinkle evenly with granulated sugar.

9. Holding all four corners of the first parchment paper, invert the cake onto the sugared parchment paper, and then carefully remove the parchment paper from the cake.

10. Let it cool completely before assembly.

The filling

1. In a stand mixer with the whisk attached, mix all of the ingredients together. Keep mixing until light and fluffy. 

Assembling the cake

1. Spread the butter cream on top of the cake and carefully roll up the cake lengthwise.

2. Place it in the refrigerator for an hour or so. It's best to slice it when it's cold to get nicer slices. But let it sit out for about 30 minutes before serving so the butter mixture will have some time to soften up.