Separate the egg whites and yolks carefully, placing them into two clean, completely grease-free bowls. Place the egg white bowl in the freezer for about 5-10 minutes.

Place mini cupcake liners in a muffin tin. Preheat your oven to 140°C (284°F) with both top and bottom heat for a full 15 minutes.

In a mixing bowl, combine 30 g of corn oil and 45 g of milk. Use a whisk to mix vigorously until the ingredients are fully combined, emulsified, and the surface looks smooth.

Sift the 25g of cake flour directly into the wet ingredients. Use the whisk to gently stir until just combined and no dry flour remains.

Add the egg yolks to the batter. Using a "Z"-shaped motion (or a gentle folding motion), stir until the batter is smooth and uniform. Be careful not to overmix or stir in circles, as this can develop gluten and make the cake tough.

Take the chilled egg whites from the freezer. Add the small amount of lemon juice.

Using an electric mixer on low speed, begin whipping until the egg whites become frothy and large bubbles (like "fish eyes") form.

Add the fine granulated sugar in 3 separate additions:

First addition: Add about one-third of the sugar. Increase the mixer speed to medium and whip until the bubbles become fine and foamy.

Second addition: Add another third of the sugar. Increase the speed to high and whip until the beaters start to leave visible trails in the meringue.

Third addition: Add the remaining sugar. Reduce the speed to low and continue whipping until you reach stiff, glossy peaks. The meringue is ready when you lift the beaters and the peaks stand straight up without drooping.

Add about one-third of the meringue to the egg yolk batter.

Use a whisk to roughly combine the two mixtures — this helps balance their densities and prevents deflation. Then, switch to a spatula and gently fold from the bottom until the batter is smooth and evenly mixed.

Pour back into remaining meringue and continue folding gently with an under-and-over motion until the batter is glossy and uniform.

Transfer the final batter to a piping bag for neat and easy filling. Pipe the batter into the prepared mini cupcake liners, filling each one to about 80% full.

Hold the filled pan firmly and tap it gently on the counter 2-3 times.

Place the pan on the middle rack of the preheated oven. Bake at 140°C (284°F) for 35-40 minutes.

The cakes are done when they spring back lightly when touched and a toothpick inserted into the center comes out clean.

As soon as they come out of the oven, tap the pan again on the counter to release steam. Then, immediately turn the cupcakes on their sides in the pan to cool. This step is critical to prevent the delicate cakes from collapsing and shrinking.

Once cooled, you can either stamp your favorite design on the surface or enjoy the cupcakes as they are.