1. Heat oven to 350°F. Lightly grease cookie sheet or line with parchment paper. Remove wrappers from peanut butter cups. Cut each peanut butter cup into 4 pieces; set aside.
2. Melt butter in medium saucepan over low heat. Add sugar and cocoa; stir to blend. Remove from heat; stir in eggs and vanilla. Stir together flour, salt and baking soda; stir into chocolate mixture. Stir in peanut butter cup pieces.*
3. Drop by heaping teaspoons onto prepared cookie sheets. Bake 10 to 12 minutes or until set and edges are firm. Do not overbake. Cool slightly; remove from cookie sheet to wire rack. Cool completely.
Makes about 48 cookies.
* For more visible peanut butter cup pieces, some of the pieces can be held back and then pushed into the cookies just as they come out of the oven.