Arrange a rack in the middle of the oven and preheat it to 350°F.
Coat a 9x13-inch baking pan with cooking spray or softened butter. Line the pan with a sheet of parchment paper that covers the bottom and extends up past the 2 long sides to form a sling.
Melt 1 stick unsalted butter in the microwave, on the stovetop, or in the warming oven. Transfer to a medium bowl.
Mix together 2 cups of Biscoff, gingersnap, or cinnamon graham cracker crumbs. Then, add 1 tablespoon of ground coffee or espresso (make sure it’s not instant) and ½ teaspoon of kosher salt. Stir to combine.
Transfer to the baking pan. Top with a sheet of parchment paper and firmly and evenly press into the bottom. Remove the parchment and set aside.
Pour 1 (14-ounce) can sweetened condensed milk over the crust and spread into an even layer.
Sprinkle evenly with 1 ½ cups roasted, salted pistachios, 1 cup semisweet or bittersweet chocolate chips, ½ cup dried tart cherries or cranberries, and ½ cup coarsely chopped candied orange peel.
Cover with the reserved parchment paper and press down firmly so the toppings stick to the condensed milk. Remove the parchment paper.
Bake until the top is lightly golden-brown, 20 to 25 minutes. Place the pan on a wire rack and let it cool completely, about 2 hours. Refrigerate for at least 30 minutes to help create smoother cuts and a gooier texture.
Run a knife around the edges of the pan to loosen the bars. Grasping the excess parchment, lift the slab out of the pan and place on a cutting board.
Cut into 24 pieces (5 cuts lengthwise, 3 cuts crosswise), or into any size squares, diamonds or rectangles you like.
The bars will keep at room temperature in an airtight container for a few days, but they are especially delicious right from the refrigerator, where they’ll keep for up to 1 week.