Preheat the oven to 375°F. Line a large baking sheet with parchment paper and set aside.
Use a hand-held mixer or stand mixer to mix together the cake mix, butter, and eggs until well combined.
15.25 ounces white cake mix, 8 tablespoons unsalted butter, 2 large eggs
Add in the peppermint (or mint) and vanilla extracts and enough green food coloring to achieve your desired color. Mix on low speed just until combined. The batter will be thick and sticky.
2 teaspoons peppermint extract, ½ teaspoon vanilla extract, green gel food coloring
In a small bowl, whisk together the powdered sugar and cornstarch.
¼ cup powdered sugar, 3 tablespoons cornstarch
Scoop the dough with a 1 1/2 tablespoon cookie scoop and roll the cookie dough balls in the powdered sugar mixture to coat. (The cookie dough itself is sticky so keep that in mind.) Place about 1 inch apart on the prepared baking sheet.
Bake for 10 to 12 minutes, or until the edges are set and the top of the cookies appear dry.
Remove the cookies from the oven and immediately place a heart-shaped sprinkle on each cookie, gently pressing it down so it sticks to the cookie.
red heart-shaped sprinkle or cinnamon
Cool the cookies on the baking sheet for 5 minutes before removing to a wire rack to cool completely.