Preheat the oven to 375°F (190°C). Line 2-3 baking sheets with parchment paper.
In a large bowl using a stand mixer or hand mixer, beat softened butter until creamy, about 1 minute.
Add cake mix and eggs to the butter. Beat on medium speed until fully combined and a soft dough forms, about 2 minutes.
Mix in peppermint and vanilla extracts until just combined.
Add green gel food coloring gradually until desired shade is reached. Remember color will lighten when baked.
In a small bowl, whisk together powdered sugar and cornstarch for coating.
Using a 1.5 tablespoon cookie scoop, portion dough into balls.
Roll each ball in the powdered sugar mixture until completely covered.
Place on prepared baking sheets, spacing cookies 2 inches apart.
Bake for 10-12 minutes until edges are set but centers still look slightly soft.
Remove from oven and immediately press one red heart into center of each cookie.
Let cool on baking sheet for 5 minutes before transferring to wire rack to cool completely.
