Place peanut butter and butter in mixer bowl. Attach bowl and flat beater to mixer. Turn to Speed 6 and beat about 1 minute, or until mixture is smooth. Stop and scrape bowl. Add sugars, egg, and vanilla. Turn to Speed 4 and beat about 1 minute. Stop and scrape bowl.
Turn to Stir Speed. Gradually add all remaining ingredients to sugar mixture and mix about 30 seconds. Turn to Speed 2 and mix about 30 seconds.
Roll dough into 1-inch balls. Place about 2 inches apart on ungreased baking sheets. Press flat with fork to criss-cross pattern to 1/4-inch thickness, if your not adding Reese's Pieces to the top.
Place peanut butter and butter in mixer bowl. Attach bowl and flat beater to mixer. Turn to Speed 6 and beat about 1 minute, or until mixture is smooth. Stop and scrape bowl. Add sugars, egg, and vanilla. Turn to Speed 4 and beat about 1 minute. Stop and scrape bowl.
Turn to Stir Speed. Gradually add all remaining ingredients to sugar mixture and mix about 30 seconds. Turn to Speed 2 and mix about 30 seconds.
Roll dough into 1-inch balls. Place about 2 inches apart on ungreased baking sheets. Press flat with fork to criss-cross pattern to 1/4-inch thickness, if your not adding Reese's Pieces to the top.