Add a tray of water in the oven (about 2 cups, to yield a moister cake), preheat oven to 200°C/395°F.
Whisk egg whites over low speed until large bubbles are formed. Add in cream of tartar, whisk until small bubbles are formed. Add in sugar gradually, whisk until stiff peak (the peaks will point straight up and hold. (Reminder: Egg whites and equipment used to beat egg whites must be grease-free, water-free and egg yolk-free. Always clean egg shells and equipment with dishwasher detergent, then dry with a clean cloth. Use a clean small bowl to separate egg yolk and egg white, if the egg yolk cracks, don’t use that egg white. When the meringue begins to look glossy, stop and check after beating for every 10 seconds, stop when it has reached the stiff peaks, do not over whip.) Combine egg yolks, sugar and salt, whisk over low speed until thick. Add in corn oil, whisk until combined. Add in milk, mix well.
Sieve together low protein flour and cocoa powder, sieve again into the wet ingredients, mix until combined.
Add meringue into batter in 3 batches, mix gently using balloon whisk.
Fold gently with spatula until well mixed, tap mixing bowl on countertop for a few times (to burst large bubbles).
Pour batter into 10″ x 14″ (25 cm x 36 cm) rectangle baking pan lined with parchment paper. Spread the batter evenly with spatula, then drop the baking pan onto countertop for a few times.
Bake at 190°C/375°F for 19-20 minutes, until the cake is golden brown. (Reminder: The cake must be baked until the top is golden brown so that the surface won’t be sticky when cooled. The heat for different oven is different, the suggested time is only for reference, adjust the baking time base on your oven if necessary.)
Drop the baking pan from 1 foot high onto countertop after removing from oven (to minimize shrinkage).
Unmould the cake, invert onto a piece of parchment paper, remove the paper at the bottom, invert again onto another piece of parchment paper, set aside to cool completely on wire rack.
Whip non-dairy topping cream until stiff, keep refrigerated for later use. (Reminder: Use stainless mixing bowl for whipping. Keep both mixing bowl and whisk in freezer for 30 minutes to chill them up before using.)
Make 2 shallow cuts on the end where rolling starts (about 1 inch apart, do not cut through).
Spread whipped non-dairy topping cream onto cake.
Roll the cake up gently.
Wrap the cake roll with cling wrap, keep refrigerated for 2 hours before slicing.
Cut Chocolate Swiss Roll Cake into 10 slices.