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 lifting.
Step 2: In a medium bowl, combine the graham cracker crumbs and melted butter. Mix until the crumbs are thoroughly moistened.
Step 3: Press the mixture evenly and firmly into the bottom of the prepared baking pan.
Step 4: Sprinkle the chopped candied mixed fruit evenly over the graham cracker crust.
Step 5: Follow with the chopped pecans or walnuts, distributing them evenly.
Step 6: Sprinkle the shredded coconut over the nuts.
Step 7: If using, sprinkle the white chocolate chips evenly over the coconut layer.
Step 8: Slowly and evenly pour the sweetened condensed milk over all the layers, ensuring it covers as much of the fruit, nuts, and coconut as possible.
Step 9: In a small bowl, combine the ground cinnamon, ground nutmeg, and allspice. Evenly sprinkle this spice mixture over the top of the sweetened condensed milk layer.
Step 10: Bake for 25-30 minutes, or until the edges are golden brown and the center is set and bubbly.
Step 11: Remove the pan from the oven and let the bars cool completely on a wire rack. This is crucial for them to set properly before cutting.
Step 12: Once completely cooled (you can chill them for an hour in the refrigerator for cleaner cuts), use the parchment paper overhang to lift the entire slab out of the pan. Place on a cutting board and slice into 24 squares or rectangles. Serve and enjoy!