In a mixing bowl, whisk together the 3 egg yolks, 4 tablespoons sugar, and ¾ cup whole milk until smooth.

Gradually whisk in the cake flour and powdered milk until no lumps remain.

Melt the unsalted butter and slowly whisk it into the egg yolk mixture.

Cook the mixture over low heat, stirring constantly, until it thickens into a custard. Let it cool completely.

In a separate large bowl, combine the snow skin premix with 1 cup boiling water and stir until a dough forms. Knead lightly until smooth.

Divide the snow skin dough into three equal portions.

To the first portion, knead in 1 teaspoon beet powder until the color is uniform. Repeat with matcha powder for the second portion and blueberry powder for the third, creating distinct colors.

Take a small piece of each colored dough (e.g., 1 tablespoon of each color) and gently press them together to create a tri-color flat disc. For a single-color mooncake, use about 1 tablespoon (15 g) dough per piece.

Flatten the tri-color dough disc. Place your desired filling (e.g., durian powder mixed with a little water to form a paste, or other traditional fillings) in the center.

Carefully wrap the dough around the filling, sealing completely.

Lightly dust a mooncake mold with cooked glutinous rice flour to prevent sticking.

Place the filled dough ball into the mold and press down firmly to create the mooncake shape.

Gently remove the mooncake from the mold. Repeat with remaining dough and filling.

Chill the finished mooncakes in the refrigerator for at least 2 hours before serving.