Beat butter, granulated sugar, brown sugar, peanut butter, egg and vanilla in large bowl until fluffy. Stir together flour, baking soda and salt; gradually add to butter mixture, beating until well blended. Stir in candies. Drop by heaping teaspoons onto ungreased cookie sheet.
Bake 10 to 12 minutes or until edges are lightly browned; remove from oven. Cool slightly; remove from pan to wire rack. Cool completely. Makes about 30 cookies.