Separate the 8 eggs into egg whites and yolks, placing them into two large bowls.

Sift 85g of cake flour and 18g of cocoa powder into a large bowl. Set aside.

Heat 85g of corn oil in a pan over low heat. Use a thermometer to measure the oil temperature, and once it reaches 70-80°C, remove from heat.

Quickly pour the hot oil into the flour mixture and stir well until it becomes smooth, free of lumps.

Add 95g of milk and continue to stir until the batter is smooth and even.

Add the 8 egg yolks and mix until the batter is silky and smooth with no graininess. Set aside.

Add 5 drops of lemon juice to the egg whites.

Gradually add the 90g of white sugar in three parts, whisking after each addition.

When the egg whites form large bubbles, add the first portion of sugar (about 30g). When bubbles become finer, add the second portion of sugar (about 30g).

When the egg whites show visible peaks, add the remaining sugar.

Continue to beat on low speed until sugar dissolves, then switch to medium-high speed until stiff peaks form, and the egg whites hold a large hook shape.

Take one-third of the whisked egg whites and gently fold it into the egg yolk mixture with a spatula, using an up-and-down motion.

Continue gently folding until fully mixed.

pour the mixed batter back into the remaining whipped egg whites and repeat the folding process until fully incorporated, and there is no visible separation between the egg whites and yolk mixture.

Pour half of the batter into the prepared baking tray and smooth it with a spatula.

Evenly sprinkle regular chocolate chips on top.

Pour the remaining batter into the tray and smooth it out again.

Decorate with heat-resistant chocolate chips on top for a beautiful finish.

Tap the tray lightly twice to settle the batter.

Place the tray into a larger tray. Fill the larger tray with 2-3 cm of water, creating a water bath.

Place it in the preheated oven and bake at 150°C for 70 minutes.

Do not open the oven door during baking to prevent temperature fluctuations that could affect the cake's texture.

After baking, use oven mitts to remove the tray and place it on a cooling rack.

While still warm, peel off the parchment paper from around the cake. Let it cool naturally.

The cake will slightly shrink as it cools. Once completely cooled, cut it into your desired portions.