Preheat oven to 375 degrees F (190 degrees C). Grease a baking sheet.
Stir together the egg, white sugar, butter, flour, cornstarch, powdered milk, baking powder, and salt in a bowl. Knead for a few minutes to make a soft dough. Divide the dough into 12 portions. Roll each portion into a ball and flatten slightly. Place on the prepared baking sheet 1 inch apart.
Bake in the preheated oven until light brown, about 10 minutes. Cool completely and store in an airtight container.
