Preheat the oven to 375 degrees F (190 degrees C) and lightly grease a baking sheet.
In a bowl, combine egg, white sugar, butter, flour, cornstarch, powdered milk, baking powder, and salt. Knead until a soft dough forms. Divide dough into 12 portions, roll each into a ball, flatten slightly, and arrange them 1 inch apart on the baking sheet.
Bake in the preheated oven for about 10 minutes until golden brown. Allow to cool completely, then store in an airtight container.