In a heavy sauce pan, heat sweetened condensed milk and peanut butter over medium low heat until a few bubbles appear,STIRRING CONSTANTLY!
Remove from heat. Stir in milk chocolate and butterscotch chips until smooth. Immediately stir in pecans and vanilla.
Spread evenly into wax paper lined 8 or 9 inch square dish. Cool in fridge until firm, about 2 hours. Turn onto smooth surface and remove paper. Cut into small squares and store in airtight container in fridge.