Preheat oven to 350 degrees. Line two baking sheets with parchment paper.
Whisk together flour, cocoa powder and salt in small bowl.
Combine the butter and 1 1/3 c of sugar and beat for 2 minutes on low speed, until fluffy. Add egg yolks, cream and vanilla; beat on low speed until combined.
Add flour mix and beat until incorporated.
For each cookie, shape a heaping tablespoon of dough into a ball and roll it in the remaining sugar to coat. Space balls 2 inches apart on baking sheets, then use your thumb to make an indentation in the top of each cookie.
Bake 10 minutes or until the edges are just set; the tops of the cookies will be soft. If indentations have lost definition, press centers again immediately after removing from oven. Transfer to cooling rack. Pipe or spoon the Nutella into the center of each cookie while cookie are still slightly warm.
Add chicken to bowl; toss to coat. (String feedback that it is better to sprinkle on both sides and massage/press it onto the chicken than just coat/toss)
Place chicken on a broiler pan coated with cooking spray. Broil chicken 5 minutes on each side.
Combine honey and vinegar in a small bowl, stirring well. Remove chicken from oven; brush 1/4 cup honey mixture on chicken. Broil 1 minute. Remove chicken from oven and turn over. Brush chicken with remaining honey mixture. Broil 1 additional minute or until chicken is done.
If you brush additional honey sauce after you broil the chicken, make sure that you don’t use contaminated sauce, so plan ahead.