Preheat oven to 325°F (165°C).
Bake Salty Egg yokes on a baking sheet 10 to 12 minutes.
Divide bean paste into 10 portions.
Roll each portion between your palms into a ball.
Make a hole in each ball with your thumb and place a baked egg yolk in each ball.
Press bean paste around yolk to cover.
Roll again to reshape into balls.
Sift together flour, baking powder and dry milk powder into a large bowl.
Repeat sifting 2 more times.
Beat eggs and sugar in another large bowl until sugar has dissolved, about 2 minutes with an electric mixer.
Add melted butter and salt.
Add flour mixture; mix to a soft dough.
Divide dough into 10 pieces and roll each piece into a ball.
Flatten each ball into a 4-inch circle between your palms.
Place a bean paste ball in the center of a circle and gather edges together to enclose filling.
Lightly flatten the top to make a round cake 2 inches wide and 1/2 inch high.
Repeat with remaining dough balls and bean paste balls.
If using a mold, press cake into mold, then tap inverted mold to remove cake.
Place cakes on a baking sheet.
Brush each cake with beaten egg yolk.
Preheat oven to 375°F (190°C).
Place a small pan of water in the oven to provide moisture and prevent the cakes from cracking.
Bake cakes 20 to 25 minutes until browned.
Remove from baking sheet with a spatula.
Cool on a rack.