Make the asado filling. Heat oil in a cooking pot. Saute onion until translucent.
Add pork. Cook until it turns light brown.
Pour-in soy sauce and water. Let boil.
Add star anise. Cook on low heat for 30 to 35 minutes.
Add sugar. Stir. Put-in Knorr liquid seasoning and ground black pepper.
Combine cornstarch and 3 tablespoons water. Mix well. Pour into the pot and cook until the sauce thickens. Set aside.
Start making the puto batter. In a large bowl, combine all purpose flour, cake flour, sugar, and baking powder. Mix well.
Add egg, evaporated milk, water, and butter. Mix all the ingredients thoroughly.
Pour about 1 tablespoons of batter mixture on each mold.
Put about 1 to 1/2 teaspoon of asado filling per mold. Add more batter until the mold is around 3/4 full.
Arrange the molds in a steamer. Steam for 2 to 3 minutes.
Top with a slice of salted duck egg. Continue steaming for 13 to 15 minutes.
Remove the molds from the steamer. Let it cool down.
Gently loosen the Puto Pao and remove from the mold. Arrange on a serving plate. Serve!