2 1/2cupsfinely ground graham cracker crumbs, about 20 crackers
1cupunsalted butter, melted
For the Filling:
1 1/3cupwalnut halves, toasted and chopped
1 1/2cup9 oz semi-sweet chocolate chips
3/4cupwhite chocolate coarsely chopped
3/4cupbutterscotch chips
3 1/4cup26 oz sweetened condensed milk
Instructions
Preheat the oven to 300 degrees F. Butter the bottom and sides of a 9-by-13-inch glass or light-colored metal baking pan. Put a long piece of parchment paper in the bottom of the pan, letting the parchment extend up the two short sides of the pan and overhang slightly on both ends. (This will make it easy to remove the bars from the pan after they have baked.) Butter the parchment.
Spread coconut on a parchment-lined baking sheet and place in preheated oven. Toast the coconut until it starts to turn golden brown, 7-10 minutes. Remove from the oven, toss, and return it to the oven for 3 more minutes.
In a large bowl, combine graham cracker crumbs and toasted coconut. Add the melted butter. Combine the mixture, then turn it out into the prepared pan. Using your hands, press the crust into an even layer on the bottom and up the sides of the pan. Use the bottom of a measuring cup to create a perfectly even crust.
Refrigerate the crust for 15 minutes, then bake for 10 minutes, or until golden brown. Transfer to a wire rack and let the crust cool completely.
To make the filling, increase the oven temperature to 325 degrees F. Evenly spread the walnuts onto the bottom of the crust. Spread the chocolate chips over the walnuts, followed by the white chocolate, followed by the butterscotch chips.
In a steady stream, pour the sweetened condensed milk evenly over the filling. Shake the pan very gently to make sure the sweetened condensed milk is evenly distributed.
Bake for 30 to 40 minutes, rotating the pan every 10 minutes, until golden brown and bubbly. Transfer to a wire rack and let cool completely. Cut into squares and serve.