Step 1: Preheat your oven to 350°F (175°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
Step 2: In a medium bowl, combine the graham cracker crumbs and melted unsalted butter. Mix until the crumbs are evenly moistened.
Step 3: Press the crumb mixture firmly and evenly into the bottom of the prepared baking pan. Use the bottom of a glass or a flat measuring cup to compact it well.
Step 4: Evenly sprinkle the semi-sweet chocolate chips over the graham cracker crust.
Step 5: Next, evenly sprinkle the butterscotch chips over the chocolate chips.
Step 6: Distribute the shredded sweetened coconut evenly over the chips.
Step 7: Finally, sprinkle the chopped pecans or walnuts evenly over the coconut layer.
Step 8: Slowly and evenly pour the entire can of sweetened condensed milk over all the layers, ensuring as much of the surface is covered as possible.
Step 9: Bake for 25-30 minutes, or until the edges are golden brown and the center is set and bubbly.
Step 10: Remove the pan from the oven and let the bars cool completely on a wire rack before cutting. For cleaner cuts, you can chill them in the refrigerator for an hour after they've cooled to room temperature.
Step 11: Once completely cooled, use the parchment paper overhang to lift the entire slab out of the pan. Place on a cutting board and cut into 24 squares or rectangles. Serve and enjoy!