Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans. This will prevent sticky situations later!

In a large bowl, combine the cake flour, cocoa powder, baking soda, baking powder, salt, and sugar. Whisk until evenly mixed. Make sure there are no lumps; you want a smooth blend for the best cake texture.

In a separate bowl, combine the canola oil, milk, and vanilla extract. Mix thoroughly before adding to your dry ingredients.

Using an electric mixer, beat the egg whites until they form stiff peaks. This step is crucial for achieving a light and airy cake; it gives the cake volume.

Gently fold the wet mixture into the dry ingredients, ensuring not to deflate the egg whites. Once mixed, fold in the egg whites with care. The batter should be light and fluffy.

Divide the batter evenly between the two prepared cake pans. Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for about 10 minutes before transferring them to a wire rack.

For the frosting, combine egg yolks, sugar, and evaporated milk in a saucepan. Cook over medium heat, stirring constantly until the mixture thickens.

Once thickened, remove it from the heat. In another bowl, combine softened butter, cornstarch, and water, mixing until creamy. Gradually add the cooled egg mixture to the butter mixture until combined.

Once your cakes are fully cooled, place one layer on a serving plate. Spread frosting generously on top. Place the second layer on top and frost the top and sides. Sprinkle chopped macadamia nuts on the sides for an inviting look.