Preheat oven to 350°. Line your cookie sheets with parchment paper and unwrap your Kisses. Melt 3 cups of the chocolate chips in a microwave safe bowl. Cool slightly.
Whisk 3 cups powdered sugar, cocoa, cornstarch, and salt in a large bowl. Set aside.
Beat egg whites in an electric mixer until they form soft peaks. Gradually beat in 1 ½ cups powdered sugar. Continue beating until fluffy and thicker (a little thinner than marshmallow crème). Beat dry ingredients into the meringue on low speed. Stir in lukewarm chocolate and remaining 1 cup of chocolate chips. The dough will seem too liquid to scoop. Give it a few minutes and it will stiffen a lot!
Place about a cup of powdered sugar in a bowl. Roll balls of cookie dough (about a tablespoon) in powdered sugar and place on prepared cookie sheets. Bake about 8-10 minutes. Immediately place one Mint Kiss on each cookie. Do not move cookies until they are completely cooled or the Kiss will collapse.
Note: This makes about 5-6 dozen cookies. I originally tripled the recipe because the yield was 18 but I ended up with way more. You could cut the recipe in half if needed.