Line square 8x8x2 inch pan with foil; set aside. Im medium micro-proof bowl microwave butter on HIGH (full power) 1 to 1.5 minute or until melted. Add cocoa; stir until smooth. Stir in confectioners' sugar and vanilla; blend well (mixture will be dry and crumbly) Stir in evaporated milk. Microwave on HIGH 1 minute; stir. Microwave and additional minute or until mixture is hot. Beat with wooden spoon until smooth; add pecan pieces. Pour into prepared pan. Store, covered, in refrigerator. Makes about 4 dozen squares.