Combine melted, cooled butter, brown sugar, and granulated sugar in a large bowl and stir until well-combined. Stir in eggs and vanilla extract. Set aside.

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

Gradually add dry ingredients to wet until completely combined.

Add mint chocolate candy pieces and mini chocolate chips and sir well.

Cover bowl with plastic wrap and refrigerate for at least 30-60 minutes.

15 minutes before you're ready to begin baking your cookies, preheat oven to 350F (175C).

Remove cookie dough from refrigerator and scoop dough by heaping 1 ½ Tablespoon-sized balls and drop onto parchment paper lined baking sheet². I like to roll the dough between my palms to get uniform, round cookies but you do not have to. Space cookie dough at least 2" apart on baking sheet.

Transfer to 350F (175C) preheated oven and bake cookies 12 minutes or until edges are light golden brown The centers of the cookies may still seem a little underdone but allow the cookies to cool completely on the baking sheet. They'll finish baking there and this is key to keeping them nice and soft.

Enjoy!