In a large bowl, using mixer, mix butter, sugars and peanut butter together until well blended. Add eggs and vanilla and mix until well blended.
Add soda, salt, and flour and mix until just combined. Don't overmix.
Add chocolate chips and 1 cup of Reese's Pieces and fold in.
Take remaining Reese's Pieces and put in a cup or bowl.
Using a large scoop, scoop a dough ball and place scooped cookie dough ball into the bowl of Reese's Pieces and press down into candies so they stick. Place candy side up of cookie on ungreased cookie sheet and slightly flatten cookie dough ball. Repeat. Place no more than 6 scoops per cookie sheet.
Bake @ 350 for 12 minutes.
Remove cookies from oven and let cool on baking sheet 5 minutes before transferring to wire rack. Makes 18 cookies.