Step 1

Preheat the oven to 350F. Grease a 12x17-inch rimmed baking sheet with baking spray or butter. Line the bottom with parchment paper and grease the paper.

Step 2

In a large mixing bowl or the bowl of a stand mixer fitted with the whisk attachment, beat the egg whites with ¼ cup sugar on high speed until stiff peaks form, about 5 minutes.

Step 3

In another large mixing bowl, combine the egg yolks, remaining ½ cup sugar, oil, vanilla, and salt. Beat on high speed until light and fluffy, about 2 minutes. Sift the flour, cocoa powder, and baking powder into the egg yolk mixture and beat on low speed just until combined.

Step 4

Fold the egg whites into the egg yolk mixture in 3 parts, until no white streaks remain. Pour the batter into the prepared baking pan and smooth into an even layer.

Step 5

Bake for 12 to 15 minutes or until the cake springs back when gently pressed.

Step 6

While the cake is baking, lay out a clean smooth kitchen towel on the counter and dust generously with cocoa powder.

Step 7

When the cake comes out of the oven, run a knife around the edges to loosen the cake from the pan. Immediately flip the cake out onto the dusted kitchen towel. Carefully peel off the parchment paper and discard. Starting at one short end, roll up the cake with the towel into a tight log. Keep the cake rolled up until completely cooled, about 2 hours.

Step 8

In a large mixing bowl, beat the cream, sugar, and vanilla on medium speed until stiff peaks form.

Step 9

Carefully unroll the cooled cake. Spread the whipped cream in an even layer over the cake. Using the towel to help, roll the cake back up into a log, carefully peeling the towel back off the cake as you roll if it is sticking anywhere. Scrape off any filling that may have squeezed out. Place the cake roll on a wire rack.

Step 10

Place the chocolate in a heat-proof mixing bowl.

Step 11

Heat the cream on the stove or in the microwave until very hot and steaming. Pour over the chocolate. Let stand for 10 minutes.

Step 12

Add the oil and stir together until smooth and well combined. If the chocolate is runny, let sit until thickened but pourable. Pour the ganache over the top of the cake and spread with a spoon to fully coat, if desired. Let stand until the ganache is mostly set, about 30 minutes. Slice and serve immediately or chill until ready to serve. Store covered and refrigerated for up to 3 days.