Step 1

Beat egg whites until foamy. Add sugar and continue beating until stiff peaks form.

Step 2

Reduce speed to low; add yolks and mix until well combined. Fold in potato starch.

Step 3

Pour into lined cookie sheet. Bake at 350 degrees Fahrenheit for 20 to 25 minutes.

Step 4

Dust a dish towel with potato starch. Invert cake onto towel. Roll up immediately. Unroll when cool.

Step 5

Beat egg whites until foamy. Add sugar and continue beating until glossy peaks form.

Step 6

In separate bowl, beat yolks, slowly adding oil until thickened. Fold egg whites into yolk mixture.

Step 7

Sift cocoa into batter, and mix gently.

Step 8

Spread filling onto cake. Reroll and place seam side down. The top may also be frosted or simply dusted with homemade confectioners sugar. Serve frozen.