Preheat oven to 350 degrees. Place oven racks to upper middle and lower middle. Line two baking sheets with parchment paper.

Whisk flour, cocoa, baking powder and salt in a bow. Place butter and chocolate in a microwave safe bowl. Heat at 50% power for 2-3 minutes, stirring frequently, until melted. Let cool slightly. Add sugar, egg, egg white, and vanilla. Whisk until well combined. Fold in dry ingredients in 3-4 additions, mixing until just combined after each addition. Once blended allow to rest for 5 minutes.

Scoop dough by 1 tablespoons and roll into balls. Place 2-inches apart on baking sheets. Bake 10 minutes until puffed. Remove trays from oven and carefully place Hershey's Kiss on top of each cookie. Return to oven and bake an additional 2 minutes.

Remove from oven and cool for 10 minutes. Then transfer to wire racks and cool completely.