Mix the pandan leaf juice with the flour in one bowl, and the coconut milk with the flour in another bowl. Strain both mixtures. Heat each mixture in a pan just until the edges start to set, then remove from heat. Use a hand mixer to blend each mixture until smooth. Both mixtures should be slightly thickened.

Use a 9-inch (22 cm) steamer tray. Cut the bottom off a water bottle and use it to help pour alternating layers of batter into the tray. Bring water to a boil in the steamer, then steam the cake for about 45 minutes.

Let the cake cool completely, then remove and cut into pieces.