Step 1

Line a 12 inch by 18 inch sheet pan with parchment paper.

Step 2

Preheat the oven to 350 F (177 C).

Step 3

Separate the egg yolks from the whites. Transfer the yolks into a large bowl. Transfer the whites into the bowl of a stand mixer.

Step 4

Using a hand mixer, beat the egg yolks on Low speed for 30 seconds or until combined. Using Medium speed, continue beating the egg yolks while gradually adding 1/2 cup sugar. (Add about 1 Tbsp sugar every 30 seconds and mix.) The mixture should be pale yellow and thick once done.

Step 5

Add the vegetable oil, milk and vanilla extract. Mix on Low speed until all wet ingredients are incorporated.

Step 6

Sift together the dry ingredients: cake flour, cocoa powder, baking powder, baking soda and salt.

Step 7

Add 1/3 of the dry ingredients to the wet ingredients and mix on Low speed until mostly incorporated. Add another 1/3 dry ingredients and continue mixing. Add the remaining 1/3 dry ingredients and mix until fully incorporated. Scrape down the bowl, working in any remaining dry ingredients.

Step 8

Using the whisk attachment for the stand mixer, beat the egg whites on Low speed for 30 seconds. Increase the speed slightly and beat for another 30 seconds or until the egg whites are foamy. Add the cream of tartar. Using Medium speed, beat the egg whites until they thicken. Gradually add the remaining 1/4 cup sugar. Continue beating on Medium High speed until the egg whites reach a firm peaks stage. (This takes a total of 3 - 3 1/2 minutes.)

Step 9

Add 1/3 beaten egg whites to the batter and gently fold until mostly incorporated. Add another 1/3 egg whites and continue folding. Add the remaining 1/3 egg whites and fold until fully incorporated.

Step 10

Transfer the batter into the lined sheet pan. Spread out the batter, pushing it to the corners of the pan. Smooth and even-out the batter using an offset spatula. Tap the pan against the counter a few times to release the air bubbles.

Step 11

Bake for 10-12 minutes. Check for doneness by touching the cake lightly with your index finger and it should spring back. Also check by inserting a toothpick and it should come out clean.

Step 12

Remove the cake from the oven. Pull the parchment paper away from the sides of the cake. Let cool for 5 minutes.

Step 13

Lay a clean kitchen towel on the work surface. Cover the towel with a generous amount of powdered sugar. Place the cake on top of the towel. Carefully remove the parchment paper by rolling it under the cake.

Step 14

Coat the cake with a generous amount of powdered sugar. Using light pressure, roll the towel and cake into a spiral. Transfer the cake with the seam-side down to a wire rack and let cool for 1 hour.

Step 15

Chill the mixing bowl and whisk in the refrigerator for 30 minutes.

Step 16

In a heat-safe measuring cup, add the water. Sprinkle the unflavored gelatin and let rest for 1 minute. Combine together. Microwave for 15 seconds. Place the cup in a bowl of cold water and let cool until the temperature is around 85 F (29 C).

Step 17

Remove the cold mixing bowl and whisk from the fridge and attach to the stand mixer. Add the cold heavy whipping cream into the bowl. Mix on Medium speed until the cream is thick, approximately 3-4 minutes. Gradually add the powdered sugar and continue mixing. Scrape down bowl.

Step 18

Add the cooled gelatin to the whipped cream. Mix on High speed until the cream is stiff, approximately 1 minute.

Step 19

Gently unroll the cooled cake. Spread a thick layer of whipped cream on the cake, coating it evenly.

Step 20

Roll up the cake, ending with seam-side down. Trim off the edges. Chill in the refrigerator until it's time to serve.

Step 21

Dust the Chocolate Roll Cake with more powdered sugar or cocoa powder.

Step 22

Cut the cake into thick slices and serve with fresh berries.

Step 23

Refrigerate any remaining cake in an air-tight container. Enjoy within the week. Freeze the cake for up to 2 months.