1. Heat oven to 350° F.
2. Beat butter, sugar and peanut butter in large bowl until well blended. Add egg and vanilla; beat well. Stir together flour, baking soda and salt; add to butter mixture, blending well. Stir in mini peanut butter cups. Drop by heaping teaspoons onto ungreased cookie sheet.
3. Bake 12 to 14 minutes or until light golden brown around the edges. Cool 1 minute; remove from cookie sheet to wire rack. Cool completely. Makes about 30 cookies.