In a heavy bottomed saucepan, combine the butter, cocoa, granulated sugar and milk. Bring mixture to a boil. Remove from heat and stir in confectioners' sugar and vanilla. Pour into a 8-in. square dish lined with tinfoil.
In microwave-safe bowl, heat caramels and bourbon on high for 1-1/4 minutes or until melted. Stir in pecan pieces; spread over chocolate layer. Microwave chocolate chips on high for 30 seconds or until melted; spread over caramel layer. Chill until firm.