Heat convection oven to 350°F. Place parchment paper on cookie sheets. Set aside.
Whip together butter and sugar until creamy.
Add eggs and vanilla, mixing until well combined.
In a separate bowl mix together flour, cocoa, baking soda, and salt. Gradually add to butter mixture, mixing until well combined.
Stir in REESE'S PIECES and chocolate chips.
Using a ¾ inch cookie dough scoop or a scant tablespoon drop dough 2 inches apart on parchment lined sheet pans.
Bake 8 to 10 minutes. Do not overbake; cookies will be soft. They will puff while baking; flatten upon cooling.
Cool slightly; remove from sheet pans to wire rack. Cool completely.
