Preheat oven to 350 degrees F, and grease a 9x13 inch pan.

Mix the melted butter and sugar until combined.

Add the eggs, one at a time, mixing well after each.

Stir in vanilla. Pour in the mochiko and add the baking powder. Stir until mostly combined.

Stir in the evaporated milk, stir in the coconut milk. When batter is totally smooth, pour into pan and bake for one hour. 

Remove from oven and allow to cool to room temperature. Remove from pan and cut into pieces on a cutting board.