Preheat oven to 325F/160C.

In a blender, add chopped pandan leaves and ¼ cup water. Blend on high. Run the pandan liquid through a sieve to remove the pulp to discard. Reserve the liquid for later.

In a large mixing bowl, add egg yolks and sugar to a bowl and beat until it turns pale yellow.

Then add the melted butter and beat until well combined.

Next add flour and only beat until just combined.

Whisk together your milk and pandan liquid. Microwave for 60 seconds until lukewarm.

Gradually add pandan milk to your egg mixture (about ¼ cup at a time). Beat until well combined.

Now beat egg whites until you reach stiff peaks.

With a spatula, fold ⅓ of the egg whites into the batter at a time until incorporated. The batter will be very runny and there will be lumps, which is fine.

Pour the batter into you square cake pan.

Bake for 60-65 minutes. At the 30 minute mark, cover loosely with aluminum foil. To check if it is cooked, insert a toothpick to check if it comes out clean. If its clean, then remove it from the oven. If not, leave it in the oven covered for another 10 minutes.

Allow to cool in the cake pan for 10 minutes, then transfer to a cooling rack.