Fill a 12-inch pan halfway with water and set over high heat.

In a bowl, sift together cake flour, sugar, baking powder and salt. Set aside.

In another bowl, combine water, egg whites and fresh milk. Using a hand mixer, beat the mixture at low speed for 5 minutes.

Add the sifted dry ingredients and blend until smooth.

Strain the batter into another bowl to ensure that there are no lumps.

Lightly brush a mini muffin tin with vegetable oil.

Fill muffin tin ¾ full with the batter.

Once the water in the pan is boiling, place the muffin tin in the pan and cover the pan with a lid.

Steam the puto for 5 minutes or until a toothpick inserted in the center of the puto comes out clean.

Once the puto is cooked, remove from the pan and allow to cool at least 30 seconds before removing from the muffin tins.

Repeat steps 6 to 10 three more times, making sure there is enough water in the pan each time.