Preheat your oven to 350°F (175°C) to ensure that your cookies bake evenly.
In a large mixing bowl, beat together the softened unsalted butter, light brown sugar, and granulated sugar using an electric mixer until creamy and fluffy, about 2-3 minutes.
Add the large egg, Greek yogurt (or sour cream), and vanilla extract to the butter mixture, beating until well combined.
In a separate bowl, whisk together the all-purpose flour, cinnamon, cornstarch, cream of tartar, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Gently fold in the cinnamon chips until evenly distributed throughout the dough.
Using a cookie scoop or tablespoon, scoop out portions of dough and place them on a baking sheet lined with parchment paper.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden and the centers look set.
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.