Preheat oven to 350°F (180°C). Line baking sheets with parchment paper.

In a bowl, whisk together flour, cornstarch, baking powder, and salt.

In a large bowl, beat butter and sugar until light and fluffy. Add egg and vanilla, mixing well.

Gradually add dry ingredients to wet mixture until combined. Roll dough into 1-inch balls.

Place dough balls on prepared baking sheets. Flatten slightly and press candy corn into the tops.

Bake for 12-15 minutes or until cookies are golden around edges. Cool on wire racks.