boil sugar & milk together for 2 1/2 minutes. turn off heat & stir in vanilla & peanut butter. line 8 x 8 glass baking dish with parchment paper. pour peanut butter mix into dish. shake & tap dish on counter to help it settle into corners & refrigerate till hard. melt chocolate & butter in microwave in 30 second increments, stirring between each one until smooth. spread over fudge & re-refrigerate until hard. pull out fudge using sides of paper & cut into equal pieces. refrigerate leftovers