Preheat the oven to 180 degree Celsius. Prepare your cake pan – grease with softened butter in all corners and dust with flour to avoid the cake from sticking to the pan while baking.
Separate the egg yolks and whites into two bowls, then add half of the sugar (35 g), in the egg yolk and the remaining half (35 g) in the egg whites.
Whisk the egg yolk and sugar mixture on high speed until it becomes pale, fluffy, and creamy. Then, whisk the egg white and sugar mixture on high speed until it reaches stiff peaks*.
In a separate bowl, measure the flour and keep it aside.
Now, you will fold the egg white mixture and the flour into the egg yolk mixture in 2 parts, alternating after each addition. Follow this order – add half of the egg white mix into the egg yolks and fold it with a silicone spatula gently until it’s well combined, then add half of the flour and fold it in until there are no streaks of flour visible, then add the remaining half of the egg white and fold it in, followed by the remaining half of the flour. Make sure you are taking your time and folding the ingredients in gently. You want to maintain the airy-ness of the egg whites so that your cake is light and fluffy and not dense. The egg white is the only raising agent in this cake, so make sure you don’t knock the air off at this point.
Transfer the cake batter into the prepared baking pan and bake for 15-20 minutes, until a toothpick comes out clean from the center and the top is golden-brown.
Once the cake is baked, take it out of the cake pan, poke holes in it using a fork and pour the prepared milk mixture on the cake while it’s still hot so that the milk can get properly absorbed into the cake. Keep adding the milk until the cake stops absorbing it, and let it chill in the fridge for at least 2 hours or overnight. Make sure to retain some milk mixture for serving.
Make the Dalgona Coffee Whipped Cream: Whip the whipping cream to medium peaks, then add the remaining HALF of the Dalgona coffee mixture and whip to stiff peaks.
Cut the cake in half horizontally to create 2 layers, then pipe a layer of the Dalgona whipped cream and top it with some of the milk mixture. Place the second cake layer on top and repeat the process. Serve the cake cold with the reserved milk mixture.