Preheat oven to 400°.
In a small bowl, mix sugar and cinnamon together, set aside.
In a medium bowl, whisk together flour, baking powder, baking soda, corn starch, and salt. Set aside.
In a large mixing bowl, beat butter and sugar until creamy. Beat in eggs and vanilla.
Add flour mixture, alternating with sour cream. Mix until combined.
Using a 1 inch cookie scoop, drop onto greased cookie sheets, 2" apart.
Lightly sprinkle with sugar/cinnamon mixture.
Place 1 mint in the center of each cookie.
Bake for 12 minutes.
Remove from oven, let cool for 2 minutes.
Place on wire rack to cool completely.