Line a 9 inch square baking pan with parchment paper, set aside.
Measure out all ingredients before you start.
Add butter, evaporated milk, brown sugar and sugar into a saucepan and place over medium heat.
Bring to a full boil, stirring constantly.
Boil 10 minutes, continuing to stir.
Remove from heat.
Add marshmallow creme and vanilla extract.
Stir until smooth.
Mix 2 cups of mixture with butterscotch chips and half of walnuts, stirring until smooth.
Mix remaining mixture with chocolate chips and walnuts, stirring until smooth.
Pour each layer into a 9 inch square pan that has been lined with parchment paper.
Chill until firm, about 4 hours.
Slice into one inch squares.
Keep refrigerated in an airtight container.