Custard cream buns recipe (sa-la-pao sai cream)

Ingredients

• 2 cups all purpose flour
• ½ cup cake flour
• ½ cup sugar
• 1 tsp salt
• ½ tsp ammonia
• 1 tbsp yeast
• 1 cup lukewarm water
• ¼ cup vegetable oil
• sheets of paper cut into 2"x2"squares, used as a base
• 5 egg yolks
• 1 cup fresh milk
• ½ cup sweetened condensed milk
• ¼ cup wheat flour
• 2 cups sugar
• ¾ cup butter