Prepare your steamer.
Combine the Egg (4) and Sweetened Condensed Milk (14 ounce) in a bowl and whisk until they are well combined.
Pour the flan into plastic molds, so they are about a third full.
Place the molds in a steamer, on low heat, for 8 minutes. Remove them from the steamer and set them aside.
Sift the All-Purpose Flour (1 cup), Granulated Sugar (1/2 cup), and Baking Powder (1/2 tablespoon) into a bowl and whisk until well combined.
Add Water (1/2 cup), Evaporated Milk (1/3 cup), Butter (2 tablespoon), and whole Egg (1). Whisk until the mixture becomes smooth and creamy.
Pour the mixture over the flan so the plastic mold is about three quarters full. Don't overfill it.
Place the molds back into the steamer for an additional 8 to 10 minutes.
Remove the puto flan from the molds.