Once the mixture starts to boil, set a timer for seven minutes. Stir and simmer for the full seven minutes. I wasn't kidding about continually stirring!
When the timer goes off, remove the pot from heat. Working quickly , pour, 1 cup of the mixture into a glass bowl before it hardens at all. Reserve the rest for later.
Add 1/2 cup of white chocolate chips and 3/4 tsp of vanilla to the mixture in the glass bowl. Stir it together until it is nice and smooth.
Return to the reserved amount of your mixture. Add 1 1/2 cups butterscotch chips, 1 tsp rum extract, and 1 tsp butter extract. Stir until the ingredients are all melted together.
Pour the fudge from the saucepan into the prepared glass pan. Spread it evenly to all corners and then cover with another piece of wax paper.
Place another layer of wax paper on top of the butterscotch fudge layer. This is the only way I could get the white vanilla layer to go on without combining too much with the butterscotch one!
Spread the vanilla fudge onto the top of the wax paper. Try to get it as close to the edges as possible.
Once the white layer is smooth and even, flip the entire layer over so that the wax paper is on top. It's just like turning a pancake! If you have trouble with this, use a second 8x8 pan. Line it with a piece of wax paper and spread the white fudge over it evenly. Then you can remove that piece of wax paper (covered in the layer of white fudge), flip it over and lay it on top of the butterscotch fudge in the other pan.
You can clean up the edges of the fudge before setting it in the fridge overnight to firm up. When you're ready to remove, use a straight edge to loosen the fudge from the sides of the pan. Overturn the pan on a cutting board to encourage the fudge to slide out. Slice the fudge into small bites since a little bit goes a long way!