Steam the soaked mung beans over high heat for about 40 minutes, until they can be easily crushed by hand. Let cool slightly, then mash with a spoon or briefly pulse in a food processor—keep a little texture if desired.

Heat a pan over low heat, add the oil, mung beans, and sugar. Stir constantly until the sugar dissolves and the mixture becomes thick, smooth, and able to hold its shape. Remove from heat and let cool completely. Divide into 15 portions (about 25g each).

In a large bowl, mix flour, sugar, salt, and yeast evenly. Gradually add milk and condensed milk while stirring. Once a shaggy dough forms, add the softened butter and knead until smooth and elastic. No need to knead to windowpane stage—just smooth and cohesive.

Divide the dough into 15 equal pieces (about 30g each) and roll into balls. Flatten one dough ball into a round wrapper with thinner edges and a slightly thicker center. Place one portion of mung bean filling in the center, seal tightly, and gently roll into a ball.

Lightly press each filled dough ball into a round cake about 1cm thick. Cover loosely with plastic wrap and let rest for 20 minutes. This step helps keep the skin soft and prevents cracking during cooking.

Heat a pan over very low heat and lightly grease it. Add the cakes, cover with a lid, and cook for about 8 minutes. Flip gently, brush a thin layer of oil on top, cover again, and cook another 8 minutes until both sides are golden. Press lightly—if it springs back, they’re done.

Remove from the pan and let cool slightly on a rack. The cakes will soften further as they cool, revealing a tender skin and a sweet, sandy mung bean center.