Line 2 large baking sheets with parchment paper or silicone baking mats and set aside.
Place 2 cups of the sifted powdered sugar in a bowl and set aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat the unsalted butter and 1 cup of the powdered sugar on medium-low speed for 1 to 2 minutes or until light and fluffy.
Add the vanilla extract and beat for an additional 30 seconds until completely incorporated.
Whisk together the all-purpose flour, cornstarch, and salt in a medium bowl.
While your mixer is on low, spoon the flour mixture slowly into the mixing bowl. You will want to allow the flour to be incorporated after each addition before adding more to the mixing bowl.
Once all your flour mixture has been added, increase the mixer speed to medium and beat the dough for an additional 30 to 45 seconds to ensure that all the ingredients are fully incorporated and that your dough is light and fluffy.
Add the green liquid food coloring and beat on low until your cookie dough is uniform in color. You can add a couple of extra drops if you want a darker green color for your dough.
Lastly, you will mix in the mini semi-sweet chocolate chips just until all the chips are fully incorporated.
Using a one tablespoon scoop, scoop out the dough and roll them into balls in the palm of your hand.
Place the rolled cookie dough balls onto the prepared cookie sheets and refrigerate the dough balls for 15 minutes.
Preheat your oven to 350°F.
Bake for 12 minutes. Allow the cookies to cool on the baking sheet for 10 minutes.
Roll each slightly warm cookie gently in the reserved bowl of powdered sugar. Place the coated cookies back on the cookie sheet to continue to cool completely. Once the cookies have cooled completely for an additional 10 to 15 minutes, you will roll each cookie in the powdered sugar for a second coating.
Place a large heart candy onto the top of each powdered sugar-coated Grinch snowball cookie.