Brush the molds with some melted butter.

In a bowl, whisk together the egg yolks, sweetened condensed milk, and vanilla extract until well combined.

Fill in about a third of each mold with the custard mixture. Steam for 5 minutes.

Meanwhile, prepare the Puto batter. First, beat the egg whites with an electric mixer until soft peak forms. Then add the fresh milk while continuously beating. Add the flour, sugar and baking powder and beat for another minute or two.

Pour some Puto batter on top of the steamed custard to fill about ¾ of the mold. Steam for another 10-12 minutes or until an inserted toothpick comes out clean.

Let them cool down a bit before removing from the molds.