Preheat the oven to 350 degrees F (175 degrees C). Line a sheet cake pan with parchment paper.

Beat 4 egg yolks and 2 tablespoons sugar together in a bowl until mixture is pale yellow and thick. Add corn oil 1 tablespoon at a time and mix well. Add milk and mix well. Sift 1/2 cup plus 2 tablespoons flour into egg yolk mixture and mix well.

Beat egg whites in a glass, metal, or ceramic bowl until foamy. Gradually add remaining 4 tablespoons sugar, continuing to beat until stiff peaks form. Add 1/3 the egg white mixture to the bowl with the egg yolk batter and fold in until mixed well. Pour egg yolk batter into the bowl with the remaining egg white mixture and fold until mixed well. Transfer batter onto the prepared sheet cake pan.

Bake in the preheated oven until top is golden brown, 15 to 20 minutes.

Remove cake from the oven and let cool until safe to handle, about 30 minutes. Dust top of cake with confectioners' sugar and flip cake over onto another piece of parchment paper. Carefully pull off the parchment paper that was on the bottom of the cake.

Spread chocolate frosting onto the cooled sheet cake and roll the cake over into a log shape. Wrap cake roll in parchment paper and place in the refrigerator.

Increase oven heat to 400 degrees F (200 degrees C). Line an 8-inch cake pan with aluminum foil or parchment paper.

Combine 3 egg yolks, 3 tablespoons sugar, cornstarch, and vanilla extract in a bowl and beat with an electric mixer until batter is pale yellow and thick; this is very important. Pour batter into the prepared pan and smooth the top.

Bake in the preheated oven, keeping a close eye on the how the color changes during baking, for 5 to 10 minutes. Remove the tiger skin from the oven immediately when the desired color is achieved. Allow tiger skin to cool completely, about 30 minutes. Flip tiger skin over and carefully remove the parchment paper that was on the bottom of the cake.

Spread vanilla frosting onto the tiger skin. Carefully remove the remaining parchment paper. Wrap the refrigerated cake roll with the tiger skin and place on a serving platter.