Directions

1. Stir the golden syrup together with 3 tablespoons of peanut oil in a small saucepan over low heat until the mixture becomes very warm, and the syrup is easy to stir, about 3 minutes. Meanwhile, whisk together the cake flour, baking soda, and salt in a mixing bowl. Stir in the golden syrup until a smooth dough forms. Wrap well with plastic wrap; refrigerate at least 4 hours.
2. Meanwhile, combine the adzuki beans and water in a large saucepan over high heat. Bring to a boil, reduce heat to medium-low, cover, and simmer until the beans are tender, about 1 hour. Drain and allow to cool for 10 minutes. Puree the beans in a blender or food processor.
3. Heat 1/4 cup of peanut oil over medium heat in the saucepan the beans were boiled in. Stir in the pureed beans along with the white sugar. Cook and stir until the bean paste clings to the stirring spoon, 10 to 20 minutes. Stir in the wheat starch. Scrape into a mixing bowl. Chill in the refrigerator until cold.
4. Preheat oven to 375 degrees F (190 degrees C). Grease a baking sheet.
5. Divide the dough and the filling each into 8 equal portions and roll into balls. Press the dough balls between your palms to form circles large enough to envelop a filling ball. Place a ball of the filling onto the center of each pastry circle, wrap the pastry around the filling, and pinch the edges together. Roll the mooncakes in the all-purpose flour to coat; shake off excess. Place the mooncakes seam-side-down onto the prepared baking sheet and press to flatten slightly.
6. Mist lightly with water. Bake in the preheated oven for 8 minutes. Remove the mooncakes from the oven and reduce the oven temperature to 300 degrees F (150 degrees C).
7. Brush with the beaten egg yolk, applying more of the yolk to to tops than to the sides. Return to the oven and bake until golden brown, about 15 minutes more. Cool completely before serving.