In a large bowl, cream butter or margarine, peanut butter, and sugar until light and fluffy. Beat in egg and vanilla. Combine flour, baking soda, and salt; blend into creamed mixture. Stir in 1 1/3 cups mini candy-coated chocolates.
Shape dough into 1 1/4 inch balls. Place about 2 inches apart on ungreased cookie sheets. Gently flatten to about 1/2 inch thickness. Place 7 to 8 of the remaining candies on each cookie; press in lightly.
Bake at 350 degrees F (175 degrees C) for 10 to 12 minutes, or until edges are light brown. Do not over bake! Cool about 1 minute on cookie sheets; transfer cookies to wire racks to cool completely.