Line your 20 cm square baking pan with parchment paper in a tall manner.
Separate your egg yolks from the whites into two bowls. Place the egg whites in a larger mixing bowl for later. The egg yolks can be placed in a smaller bowl.
In another large mixing bowl, sift together all purpose flour and corn starch. Whisk until well combined.
Heat your avocado oil in the microwave for 80 seconds until it's 90 degrees C using a thermometer to measure the temperature.
Then immediately pour the hot oil into the flour mixture and mix well. Add in half the portion of your milk into the flour mixture and mix until combined.
Then mix in your egg yolks into the batter. Followed by the rest of your milk.
The batter should be viscose and a bit runny. Set the batter aside.
Preheat your oven at 300 degrees F.
Using an electric whisk, whisk your egg whites and add your white sugar to it in three portions.
The meringue should reach a soft peak, not a stiff peak or this will cause large cracks in your cake. If you under whisk, you cake will have dents. In order to tell if it's a soft peak, stir your meringue with the whisk and lift it up. If it forms a wiggly tail at the end of your whisk that doesn't fall, your meringue is ready.
Gently whisk a large dollop of the meringue into the yellow batter until combined. Then add another dollop and whisk again.
Then pour the rest of your meringue and gently whisk until it's just combined.
Switch to a spatula to mix and fold the batter, scraping the base of the bowl to ensure it's thoroughly mixed properly.
Pour the batter into your lined baking pan. Tap the pan on a table to release any bubbles and smooth out the top with a spatula.
Place the square pan with your cake batter into a larger baking dish filled with 70 degrees C hot water.
Bake the cake for 85 minutes until you poke it with a toothpick and it comes out clean.
Remove the parchment paper and slice the cake while hot. This cake can be served warm or cold.