Bring a small pot of water to boil and turn off the heat.
Place egg yolks and caster sugar in a heatproof bowl and whisk with a wire whisk until combined (the sugar doesn't have to dissolve).
50 grams egg yolks, 15 grams caster sugar
Place the bowl above the pot of water (the hot water should not be touching the base of the heatproof bowl). Whisk constantly until the mixture reaches 45°C. Remove the heatproof bowl from heat immediately.
Whisk constantly and more vigorously with the wire whisk for 3 to 5 minutes until the mixture lightens in colour, thickens, and leaves a trail when the wire whisk is lifted from the batter.
Whisk in the oil in two batches, whisking vigorously for about 30 seconds each time to ensure the oil is completely emulsified with the batter.
40 grams vegetable oil
Add in the milk and whisk (less vigorously as the batter will splatter out) until incorporated and foamy.
80 grams milk
Add in the flour mixture and whisk gently until just incorporated. Use a spatula and fold a few times, scrapping the bottom of the bowl to ensure the batter is mixed together.
Egg White Batter
Get ready an electric mixer. Take out the chilled egg whites from the refrigerator and add in the salt. Beat on med-low speed until the egg whites are foamy.
150 grams egg whites, Pinch salt
Add in the sugar all at one go and beat immediately on medium-high speed with the electric mixer.
40 grams caster sugar
When the egg whites become white in colour (opaque) and forming streaks, stop and assess the egg whites.
Lift up the egg whites, if the egg whites are still liquid-y and cannot hold any shape, continue beating on med-high speed for 30 seconds to 1 minute and assess again.
If the egg whites can be lifted but the tip flop and fold over, beat on low speed, checking every 30 seconds, until the egg whites can be lifted but the tip will bend slightly. The egg white mixture should be shiny, airy yet still soft. Do not beat until the egg whites form stiff peaks.
Remove the electric mixer's beaters. Manually use the beaters to whisk through the egg whites, combing the sides especially, for 30 seconds to mix them altogether.
Mixing the Batters Together
Scoop one-third of the egg whites into the egg yolk batter. Fold gently with a wire whisk. Scoop another third of the egg whites and fold into the egg egg yolk batter.
Pour the egg yolk batter into the remaining egg whites. Fold the batters together.
Once all the egg whites are folded in, use a rubber spatula and fold a few more times, scraping the sides and bottom of the mixing bowl to ensure the batter is mixed together.
Baking the Chiffon Cake
Position the mixing bowl just above the cake tin and pour in the batter slowly, rotating the tin so that it fills up evenly. Use a spatula and scrape in remaining batter. Lift up the chiffon tin about 3 to 5-cm from the countertop and drop it 3 times to get rid of large air bubbles.
Lower the oven temperature to 180°C (conventional) / 170°C (convectional). Bake for 30 to 35 minutes in the centre of the oven until a skewer inserted into the centre of the chiffon comes out clean.
Lift up the chiffon tin about 3 to 5-cm from the countertop and drop it 3 times, then immediately invert the chiffon tin and balance the tin on a rack or small ramekin, as long as the rack / ramekin does not touch the surface of the cake. Let the chiffon cake cool completely upside down.
Unmould the Chiffon Cake
Using your fingers, gently pull the cake a little bit away from the tin. This will allow the spatula to slide in more easily.
Slide a thin spatula between the tin and the inner circumference of the cake. Use a zig zag motion to loosen the cake.
Place the tin on its side on the countertop. Slide the spatula between the tin and the outer circumference of the cake. Using one hand to hold the spatula firmly downwards, rotate the tin to loosen the cake.
Lift out the cake. Use your fingers and gently pull the base of the cake away from the base of the tin to allow the spatula to slide in more easily.
Place the cake on the countertop. Slide the spatula between the tin and the base of the cake. Using one hand to hold the spatula firmly downwards, rotate the tin to loosen the cake.
Invert the cake onto a cake board. It should slide out easily.
Cream Cheese Whipped Cream (optional)
Place cream cheese and icing sugar in a mixing bowl. Mix with a spatula until the icing sugar is no longer visible.
50 grams cream cheese, 30 grams icing sugar
Beat with a mixer on medium speed until the cream cheese mixture is very smooth and fluffy.
Pour in the very cold cream and beat on medium-high speed until stiff peaks are formed. Beat in the vanilla at low speed until incorporated. Use immediately.
100 grams whipping cream, 1 teaspoon vanilla
Filling the Chiffon Cake (optional)
Fit a piping bag with a coupler - this makes it easier to change piping tips later on.
Using the piping tip used to fill cream puffs, poke 8 holes into the chiffon cake. Alternatively, use a straw to poke the holes. Fit this piping tip onto the piping bag.
Fill the piping bag with the cream cheese whipped cream. Fill the holes with the filling, reserving some for decoration.
Change the piping tip to a star tip and pipe swirls over the holes to cover them.
Decorate with gold foil or with fruits as desired. Chill the cake for about 15 to 30 minutes for the filling to firm up slightly before serving.
NOTES
Please go through the step-by-step above for the full details and explanations on why certain steps are done in a certain way.